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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 A <tt>.deb</tt> package contains two sets of files: a set of files
807 to install on the system when the package is installed, and a set
808 of files that provide additional metadata about the package or
809 which are executed when the package is installed or removed. This
810 second set of files is called <em>control information files</em>.
811 Among those files are the package maintainer scripts
812 and <file>control</file>, the <qref id="binarycontrolfiles">binary
813 package control file</qref> that contains the control fields for
814 the package. Other control information files
815 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
816 file</qref> used to store shared library dependency information
817 and the <file>conffiles</file> file that lists the package's
818 configuration files (described in <ref id="config-files">).
822 There is unfortunately a collision of terminology here between
823 control information files and files in the Debian control file
824 format. Throughout this document, a <em>control file</em> refers
825 to a file in the Debian control file format. These files are
826 documented in <ref id="controlfields">. Only files referred to
827 specifically as <em>control information files</em> are the files
828 included in the control information file member of
829 the <file>.deb</file> file format used by binary packages. Most
830 control information files are not in the Debian control file
835 <heading>The package name</heading>
838 Every package must have a name that's unique within the Debian
843 The package name is included in the control field
844 <tt>Package</tt>, the format of which is described
845 in <ref id="f-Package">.
846 The package name is also included as a part of the file name
847 of the <tt>.deb</tt> file.
852 <heading>The version of a package</heading>
855 Every package has a version number recorded in its
856 <tt>Version</tt> control file field, described in
857 <ref id="f-Version">.
861 The package management system imposes an ordering on version
862 numbers, so that it can tell whether packages are being up- or
863 downgraded and so that package system front end applications
864 can tell whether a package it finds available is newer than
865 the one installed on the system. The version number format
866 has the most significant parts (as far as comparison is
867 concerned) at the beginning.
871 If an upstream package has problematic version numbers they
872 should be converted to a sane form for use in the
873 <tt>Version</tt> field.
877 <heading>Version numbers based on dates</heading>
880 In general, Debian packages should use the same version
881 numbers as the upstream sources. However, upstream version
882 numbers based on some date formats (sometimes used for
883 development or "snapshot" releases) will not be ordered
884 correctly by the package management software. For
885 example, <prgn>dpkg</prgn> will consider "96May01" to be
886 greater than "96Dec24".
890 To prevent having to use epochs for every new upstream
891 version, the date-based portion of any upstream version number
892 should be given in a way that sorts correctly: four-digit year
893 first, followed by a two-digit numeric month, followed by a
894 two-digit numeric date, possibly with punctuation between the
899 Native Debian packages (i.e., packages which have been written
900 especially for Debian) whose version numbers include dates
901 should also follow these rules. If punctuation is desired
902 between the date components, remember that hyphen (<tt>-</tt>)
903 cannot be used in native package versions. Period
904 (<tt>.</tt>) is normally a good choice.
911 <heading>The maintainer of a package</heading>
914 Every package must have a Debian maintainer (the
915 maintainer may be one person or a group of people
916 reachable from a common email address, such as a mailing
917 list). The maintainer is responsible for ensuring that
918 the package is placed in the appropriate distributions.
922 The maintainer must be specified in the
923 <tt>Maintainer</tt> control field with their correct name
924 and a working email address. If one person maintains
925 several packages, they should try to avoid having
926 different forms of their name and email address in
927 the <tt>Maintainer</tt> fields of those packages.
931 The format of the <tt>Maintainer</tt> control field is
932 described in <ref id="f-Maintainer">.
936 If the maintainer of a package quits from the Debian
937 project, "Debian QA Group"
938 <email>packages@qa.debian.org</email> takes over the
939 maintainer-ship of the package until someone else
940 volunteers for that task. These packages are called
941 <em>orphaned packages</em>.<footnote>
942 The detailed procedure for doing this gracefully can
943 be found in the Debian Developer's Reference,
944 see <ref id="related">.
949 <sect id="descriptions">
950 <heading>The description of a package</heading>
953 Every Debian package must have a <tt>Description</tt> control
954 field which contains a synopsis and extended description of the
955 package. Technical information about the format of the
956 <tt>Description</tt> field is in <ref id="f-Description">.
960 The description should describe the package (the program) to a
961 user (system administrator) who has never met it before so that
962 they have enough information to decide whether they want to
963 install it. This description should not just be copied verbatim
964 from the program's documentation.
968 Put important information first, both in the synopsis and
969 extended description. Sometimes only the first part of the
970 synopsis or of the description will be displayed. You can
971 assume that there will usually be a way to see the whole
972 extended description.
976 The description should also give information about the
977 significant dependencies and conflicts between this package
978 and others, so that the user knows why these dependencies and
979 conflicts have been declared.
983 Instructions for configuring or using the package should
984 not be included (that is what installation scripts,
985 manual pages, info files, etc., are for). Copyright
986 statements and other administrivia should not be included
987 either (that is what the copyright file is for).
990 <sect1 id="synopsis"><heading>The single line synopsis</heading>
993 The single line synopsis should be kept brief - certainly
998 Do not include the package name in the synopsis line. The
999 display software knows how to display this already, and you
1000 do not need to state it. Remember that in many situations
1001 the user may only see the synopsis line - make it as
1002 informative as you can.
1007 <sect1 id="extendeddesc"><heading>The extended description</heading>
1010 Do not try to continue the single line synopsis into the
1011 extended description. This will not work correctly when
1012 the full description is displayed, and makes no sense
1013 where only the summary (the single line synopsis) is
1018 The extended description should describe what the package
1019 does and how it relates to the rest of the system (in terms
1020 of, for example, which subsystem it is which part of).
1024 The description field needs to make sense to anyone, even
1025 people who have no idea about any of the things the
1026 package deals with.<footnote>
1027 The blurb that comes with a program in its
1028 announcements and/or <prgn>README</prgn> files is
1029 rarely suitable for use in a description. It is
1030 usually aimed at people who are already in the
1031 community where the package is used.
1040 <heading>Dependencies</heading>
1043 Every package must specify the dependency information
1044 about other packages that are required for the first to
1049 For example, a dependency entry must be provided for any
1050 shared libraries required by a dynamically-linked executable
1051 binary in a package.
1055 Packages are not required to declare any dependencies they
1056 have on other packages which are marked <tt>Essential</tt>
1057 (see below), and should not do so unless they depend on a
1058 particular version of that package.<footnote>
1060 Essential is needed in part to avoid unresolvable dependency
1061 loops on upgrade. If packages add unnecessary dependencies
1062 on packages in this set, the chances that there
1063 <strong>will</strong> be an unresolvable dependency loop
1064 caused by forcing these Essential packages to be configured
1065 first before they need to be is greatly increased. It also
1066 increases the chances that frontends will be unable to
1067 <strong>calculate</strong> an upgrade path, even if one
1071 Also, functionality is rarely ever removed from the
1072 Essential set, but <em>packages</em> have been removed from
1073 the Essential set when the functionality moved to a
1074 different package. So depending on these packages <em>just
1075 in case</em> they stop being essential does way more harm
1082 Sometimes, a package requires another package to be installed
1083 <em>and</em> configured before it can be installed. In this
1084 case, you must specify a <tt>Pre-Depends</tt> entry for
1089 You should not specify a <tt>Pre-Depends</tt> entry for a
1090 package before this has been discussed on the
1091 <tt>debian-devel</tt> mailing list and a consensus about
1092 doing that has been reached.
1096 The format of the package interrelationship control fields is
1097 described in <ref id="relationships">.
1101 <sect id="virtual_pkg">
1102 <heading>Virtual packages</heading>
1105 Sometimes, there are several packages which offer
1106 more-or-less the same functionality. In this case, it's
1107 useful to define a <em>virtual package</em> whose name
1108 describes that common functionality. (The virtual
1109 packages only exist logically, not physically; that's why
1110 they are called <em>virtual</em>.) The packages with this
1111 particular function will then <em>provide</em> the virtual
1112 package. Thus, any other package requiring that function
1113 can simply depend on the virtual package without having to
1114 specify all possible packages individually.
1118 All packages should use virtual package names where
1119 appropriate, and arrange to create new ones if necessary.
1120 They should not use virtual package names (except privately,
1121 amongst a cooperating group of packages) unless they have
1122 been agreed upon and appear in the list of virtual package
1123 names. (See also <ref id="virtual">)
1127 The latest version of the authoritative list of virtual
1128 package names can be found in the <tt>debian-policy</tt> package.
1129 It is also available from the Debian web mirrors at
1130 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1131 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1135 The procedure for updating the list is described in the preface
1142 <heading>Base system</heading>
1145 The <tt>base system</tt> is a minimum subset of the Debian
1146 GNU/Linux system that is installed before everything else
1147 on a new system. Only very few packages are allowed to form
1148 part of the base system, in order to keep the required disk
1153 The base system consists of all those packages with priority
1154 <tt>required</tt> or <tt>important</tt>. Many of them will
1155 be tagged <tt>essential</tt> (see below).
1160 <heading>Essential packages</heading>
1163 Essential is defined as the minimal set of functionality that
1164 must be available and usable on the system at all times, even
1165 when packages are in an unconfigured (but unpacked) state.
1166 Packages are tagged <tt>essential</tt> for a system using the
1167 <tt>Essential</tt> control field. The format of the
1168 <tt>Essential</tt> control field is described in <ref
1173 Since these packages cannot be easily removed (one has to
1174 specify an extra <em>force option</em> to
1175 <prgn>dpkg</prgn> to do so), this flag must not be used
1176 unless absolutely necessary. A shared library package
1177 must not be tagged <tt>essential</tt>; dependencies will
1178 prevent its premature removal, and we need to be able to
1179 remove it when it has been superseded.
1183 Since dpkg will not prevent upgrading of other packages
1184 while an <tt>essential</tt> package is in an unconfigured
1185 state, all <tt>essential</tt> packages must supply all of
1186 their core functionality even when unconfigured. If the
1187 package cannot satisfy this requirement it must not be
1188 tagged as essential, and any packages depending on this
1189 package must instead have explicit dependency fields as
1194 Maintainers should take great care in adding any programs,
1195 interfaces, or functionality to <tt>essential</tt> packages.
1196 Packages may assume that functionality provided by
1197 <tt>essential</tt> packages is always available without
1198 declaring explicit dependencies, which means that removing
1199 functionality from the Essential set is very difficult and is
1200 almost never done. Any capability added to an
1201 <tt>essential</tt> package therefore creates an obligation to
1202 support that capability as part of the Essential set in
1207 You must not tag any packages <tt>essential</tt> before
1208 this has been discussed on the <tt>debian-devel</tt>
1209 mailing list and a consensus about doing that has been
1214 <sect id="maintscripts">
1215 <heading>Maintainer Scripts</heading>
1218 The package installation scripts should avoid producing
1219 output which is unnecessary for the user to see and
1220 should rely on <prgn>dpkg</prgn> to stave off boredom on
1221 the part of a user installing many packages. This means,
1222 amongst other things, using the <tt>--quiet</tt> option on
1223 <prgn>install-info</prgn>.
1227 Errors which occur during the execution of an installation
1228 script must be checked and the installation must not
1229 continue after an error.
1233 Note that in general <ref id="scripts"> applies to package
1234 maintainer scripts, too.
1238 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1239 to another package without consulting the maintainer of that
1240 package first. When adding or removing diversions, package
1241 maintainer scripts must provide the <tt>--package</tt> flag
1242 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1246 All packages which supply an instance of a common command
1247 name (or, in general, filename) should generally use
1248 <prgn>update-alternatives</prgn>, so that they may be
1249 installed together. If <prgn>update-alternatives</prgn>
1250 is not used, then each package must use
1251 <tt>Conflicts</tt> to ensure that other packages are
1252 de-installed. (In this case, it may be appropriate to
1253 specify a conflict against earlier versions of something
1254 that previously did not use
1255 <prgn>update-alternatives</prgn>; this is an exception to
1256 the usual rule that versioned conflicts should be
1260 <sect1 id="maintscriptprompt">
1261 <heading>Prompting in maintainer scripts</heading>
1263 Package maintainer scripts may prompt the user if
1264 necessary. Prompting must be done by communicating
1265 through a program, such as <prgn>debconf</prgn>, which
1266 conforms to the Debian Configuration Management
1267 Specification, version 2 or higher.
1271 Packages which are essential, or which are dependencies of
1272 essential packages, may fall back on another prompting method
1273 if no such interface is available when they are executed.
1277 The Debian Configuration Management Specification is included
1278 in the <file>debconf_specification</file> files in the
1279 <package>debian-policy</package> package.
1280 It is also available from the Debian web mirrors at
1281 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1282 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1286 Packages which use the Debian Configuration Management
1287 Specification may contain the additional control information
1288 files <file>config</file>
1289 and <file>templates</file>. <file>config</file> is an
1290 additional maintainer script used for package configuration,
1291 and <file>templates</file> contains templates used for user
1292 prompting. The <prgn>config</prgn> script might be run before
1293 the <prgn>preinst</prgn> script and before the package is
1294 unpacked or any of its dependencies or pre-dependencies are
1295 satisfied. Therefore it must work using only the tools
1296 present in <em>essential</em> packages.<footnote>
1297 <package>Debconf</package> or another tool that
1298 implements the Debian Configuration Management
1299 Specification will also be installed, and any
1300 versioned dependencies on it will be satisfied
1301 before preconfiguration begins.
1306 Packages which use the Debian Configuration Management
1307 Specification must allow for translation of their user-visible
1308 messages by using a gettext-based system such as the one
1309 provided by the <package>po-debconf</package> package.
1313 Packages should try to minimize the amount of prompting
1314 they need to do, and they should ensure that the user
1315 will only ever be asked each question once. This means
1316 that packages should try to use appropriate shared
1317 configuration files (such as <file>/etc/papersize</file> and
1318 <file>/etc/news/server</file>), and shared
1319 <package>debconf</package> variables rather than each
1320 prompting for their own list of required pieces of
1325 It also means that an upgrade should not ask the same
1326 questions again, unless the user has used
1327 <tt>dpkg --purge</tt> to remove the package's configuration.
1328 The answers to configuration questions should be stored in an
1329 appropriate place in <file>/etc</file> so that the user can
1330 modify them, and how this has been done should be
1335 If a package has a vitally important piece of
1336 information to pass to the user (such as "don't run me
1337 as I am, you must edit the following configuration files
1338 first or you risk your system emitting badly-formatted
1339 messages"), it should display this in the
1340 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1341 prompt the user to hit return to acknowledge the
1342 message. Copyright messages do not count as vitally
1343 important (they belong in
1344 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1345 neither do instructions on how to use a program (these
1346 should be in on-line documentation, where all the users
1351 Any necessary prompting should almost always be confined
1352 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1353 script. If it is done in the <prgn>postinst</prgn>, it
1354 should be protected with a conditional so that
1355 unnecessary prompting doesn't happen if a package's
1356 installation fails and the <prgn>postinst</prgn> is
1357 called with <tt>abort-upgrade</tt>,
1358 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1368 <heading>Source packages</heading>
1370 <sect id="standardsversion">
1371 <heading>Standards conformance</heading>
1374 Source packages should specify the most recent version number
1375 of this policy document with which your package complied
1376 when it was last updated.
1380 This information may be used to file bug reports
1381 automatically if your package becomes too much out of date.
1385 The version is specified in the <tt>Standards-Version</tt>
1387 The format of the <tt>Standards-Version</tt> field is
1388 described in <ref id="f-Standards-Version">.
1392 You should regularly, and especially if your package has
1393 become out of date, check for the newest Policy Manual
1394 available and update your package, if necessary. When your
1395 package complies with the new standards you should update the
1396 <tt>Standards-Version</tt> source package field and
1397 release it.<footnote>
1398 See the file <file>upgrading-checklist</file> for
1399 information about policy which has changed between
1400 different versions of this document.
1406 <sect id="pkg-relations">
1407 <heading>Package relationships</heading>
1410 Source packages should specify which binary packages they
1411 require to be installed or not to be installed in order to
1412 build correctly. For example, if building a package
1413 requires a certain compiler, then the compiler should be
1414 specified as a build-time dependency.
1418 It is not necessary to explicitly specify build-time
1419 relationships on a minimal set of packages that are always
1420 needed to compile, link and put in a Debian package a
1421 standard "Hello World!" program written in C or C++. The
1422 required packages are called <em>build-essential</em>, and
1423 an informational list can be found in
1424 <file>/usr/share/doc/build-essential/list</file> (which is
1425 contained in the <tt>build-essential</tt>
1428 <list compact="compact">
1430 This allows maintaining the list separately
1431 from the policy documents (the list does not
1432 need the kind of control that the policy
1436 Having a separate package allows one to install
1437 the build-essential packages on a machine, as
1438 well as allowing other packages such as tasks to
1439 require installation of the build-essential
1440 packages using the depends relation.
1443 The separate package allows bug reports against
1444 the list to be categorized separately from
1445 the policy management process in the BTS.
1452 When specifying the set of build-time dependencies, one
1453 should list only those packages explicitly required by the
1454 build. It is not necessary to list packages which are
1455 required merely because some other package in the list of
1456 build-time dependencies depends on them.<footnote>
1457 The reason for this is that dependencies change, and
1458 you should list all those packages, and <em>only</em>
1459 those packages that <em>you</em> need directly. What
1460 others need is their business. For example, if you
1461 only link against <file>libimlib</file>, you will need to
1462 build-depend on <package>libimlib2-dev</package> but
1463 not against any <tt>libjpeg*</tt> packages, even
1464 though <tt>libimlib2-dev</tt> currently depends on
1465 them: installation of <package>libimlib2-dev</package>
1466 will automatically ensure that all of its run-time
1467 dependencies are satisfied.
1472 If build-time dependencies are specified, it must be
1473 possible to build the package and produce working binaries
1474 on a system with only essential and build-essential
1475 packages installed and also those required to satisfy the
1476 build-time relationships (including any implied
1477 relationships). In particular, this means that version
1478 clauses should be used rigorously in build-time
1479 relationships so that one cannot produce bad or
1480 inconsistently configured packages when the relationships
1481 are properly satisfied.
1485 <ref id="relationships"> explains the technical details.
1490 <heading>Changes to the upstream sources</heading>
1493 If changes to the source code are made that are not
1494 specific to the needs of the Debian system, they should be
1495 sent to the upstream authors in whatever form they prefer
1496 so as to be included in the upstream version of the
1501 If you need to configure the package differently for
1502 Debian or for Linux, and the upstream source doesn't
1503 provide a way to do so, you should add such configuration
1504 facilities (for example, a new <prgn>autoconf</prgn> test
1505 or <tt>#define</tt>) and send the patch to the upstream
1506 authors, with the default set to the way they originally
1507 had it. You can then easily override the default in your
1508 <file>debian/rules</file> or wherever is appropriate.
1512 You should make sure that the <prgn>configure</prgn> utility
1513 detects the correct architecture specification string
1514 (refer to <ref id="arch-spec"> for details).
1518 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1519 <prgn>configure</prgn> scripts are used, you should edit the
1520 <file>.in</file> files rather than editing the
1521 <prgn>Makefile</prgn> directly. This allows the user to
1522 reconfigure the package if necessary. You should
1523 <em>not</em> configure the package and edit the generated
1524 <prgn>Makefile</prgn>! This makes it impossible for someone
1525 else to later reconfigure the package without losing the
1531 <sect id="dpkgchangelog">
1532 <heading>Debian changelog: <file>debian/changelog</file></heading>
1535 Changes in the Debian version of the package should be
1536 briefly explained in the Debian changelog file
1537 <file>debian/changelog</file>.<footnote>
1539 Mistakes in changelogs are usually best rectified by
1540 making a new changelog entry rather than "rewriting
1541 history" by editing old changelog entries.
1544 This includes modifications
1545 made in the Debian package compared to the upstream one
1546 as well as other changes and updates to the package.
1548 Although there is nothing stopping an author who is also
1549 the Debian maintainer from using this changelog for all
1550 their changes, it will have to be renamed if the Debian
1551 and upstream maintainers become different people. In such
1552 a case, however, it might be better to maintain the package
1553 as a non-native package.
1558 The format of the <file>debian/changelog</file> allows the
1559 package building tools to discover which version of the package
1560 is being built and find out other release-specific information.
1564 That format is a series of entries like this:
1566 <example compact="compact">
1567 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1569 [optional blank line(s), stripped]
1571 * <var>change details</var>
1572 <var>more change details</var>
1574 [blank line(s), included in output of dpkg-parsechangelog]
1576 * <var>even more change details</var>
1578 [optional blank line(s), stripped]
1580 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1585 <var>package</var> and <var>version</var> are the source
1586 package name and version number.
1590 <var>distribution(s)</var> lists the distributions where
1591 this version should be installed when it is uploaded - it
1592 is copied to the <tt>Distribution</tt> field in the
1593 <file>.changes</file> file. See <ref id="f-Distribution">.
1597 <var>urgency</var> is the value for the <tt>Urgency</tt>
1598 field in the <file>.changes</file> file for the upload
1599 (see <ref id="f-Urgency">). It is not possible to specify
1600 an urgency containing commas; commas are used to separate
1601 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1602 <prgn>dpkg</prgn> changelog format (though there is
1603 currently only one useful <var>keyword</var>,
1608 The change details may in fact be any series of lines
1609 starting with at least two spaces, but conventionally each
1610 change starts with an asterisk and a separating space and
1611 continuation lines are indented so as to bring them in
1612 line with the start of the text above. Blank lines may be
1613 used here to separate groups of changes, if desired.
1617 If this upload resolves bugs recorded in the Bug Tracking
1618 System (BTS), they may be automatically closed on the
1619 inclusion of this package into the Debian archive by
1620 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1621 in the change details.<footnote>
1622 To be precise, the string should match the following
1623 Perl regular expression:
1625 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1627 Then all of the bug numbers listed will be closed by the
1628 archive maintenance script (<prgn>katie</prgn>) using the
1629 <var>version</var> of the changelog entry.
1631 This information is conveyed via the <tt>Closes</tt> field
1632 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1636 The maintainer name and email address used in the changelog
1637 should be the details of the person uploading <em>this</em>
1638 version. They are <em>not</em> necessarily those of the
1639 usual package maintainer. The information here will be
1640 copied to the <tt>Changed-By</tt> field in the
1641 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1642 and then later used to send an acknowledgement when the
1643 upload has been installed.
1647 The <var>date</var> has the following format<footnote>
1648 This is the same as the format generated by <tt>date
1650 </footnote> (compatible and with the same semantics of
1651 RFC 2822 and RFC 5322):
1652 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1654 <list compact="compact">
1656 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1659 dd is a one- or two-digit day of the month (01-31)
1662 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1665 <item>yyyy is the four-digit year (e.g. 2010)</item>
1666 <item>hh is the two-digit hour (00-23)</item>
1667 <item>mm is the two-digit minutes (00-59)</item>
1668 <item>ss is the two-digit seconds (00-60)</item>
1670 +zzzz or -zzzz is the the time zone offset from Coordinated
1671 Universal Time (UTC). "+" indicates that the time is ahead
1672 of (i.e., east of) UTC and "-" indicates that the time is
1673 behind (i.e., west of) UTC. The first two digits indicate
1674 the hour difference from UTC and the last two digits
1675 indicate the number of additional minutes difference from
1676 UTC. The last two digits must be in the range 00-59.
1682 The first "title" line with the package name must start
1683 at the left hand margin. The "trailer" line with the
1684 maintainer and date details must be preceded by exactly
1685 one space. The maintainer details and the date must be
1686 separated by exactly two spaces.
1690 The entire changelog must be encoded in UTF-8.
1694 For more information on placement of the changelog files
1695 within binary packages, please see <ref id="changelogs">.
1699 <sect id="dpkgcopyright">
1700 <heading>Copyright: <file>debian/copyright</file></heading>
1702 Every package must be accompanied by a verbatim copy of its
1703 copyright information and distribution license in the file
1704 <file>/usr/share/doc/<var>package</var>/copyright</file>
1705 (see <ref id="copyrightfile"> for further details). Also see
1706 <ref id="pkgcopyright"> for further considerations related
1707 to copyrights for packages.
1711 <heading>Error trapping in makefiles</heading>
1714 When <prgn>make</prgn> invokes a command in a makefile
1715 (including your package's upstream makefiles and
1716 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1717 means that <prgn>sh</prgn>'s usual bad error handling
1718 properties apply: if you include a miniature script as one
1719 of the commands in your makefile you'll find that if you
1720 don't do anything about it then errors are not detected
1721 and <prgn>make</prgn> will blithely continue after
1726 Every time you put more than one shell command (this
1727 includes using a loop) in a makefile command you
1728 must make sure that errors are trapped. For
1729 simple compound commands, such as changing directory and
1730 then running a program, using <tt>&&</tt> rather
1731 than semicolon as a command separator is sufficient. For
1732 more complex commands including most loops and
1733 conditionals you should include a separate <tt>set -e</tt>
1734 command at the start of every makefile command that's
1735 actually one of these miniature shell scripts.
1739 <sect id="timestamps">
1740 <heading>Time Stamps</heading>
1742 Maintainers should preserve the modification times of the
1743 upstream source files in a package, as far as is reasonably
1745 The rationale is that there is some information conveyed
1746 by knowing the age of the file, for example, you could
1747 recognize that some documentation is very old by looking
1748 at the modification time, so it would be nice if the
1749 modification time of the upstream source would be
1755 <sect id="restrictions">
1756 <heading>Restrictions on objects in source packages</heading>
1759 The source package may not contain any hard links<footnote>
1761 This is not currently detected when building source
1762 packages, but only when extracting
1766 Hard links may be permitted at some point in the
1767 future, but would require a fair amount of
1770 </footnote>, device special files, sockets or setuid or
1771 setgid files.<footnote>
1772 Setgid directories are allowed.
1777 <sect id="debianrules">
1778 <heading>Main building script: <file>debian/rules</file></heading>
1781 This file must be an executable makefile, and contains the
1782 package-specific recipes for compiling the package and
1783 building binary package(s) from the source.
1787 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1788 so that it can be invoked by saying its name rather than
1789 invoking <prgn>make</prgn> explicitly. That is, invoking
1790 either of <tt>make -f debian/rules <em>args...</em></tt>
1791 or <tt>./debian/rules <em>args...</em></tt> must result in
1796 Since an interactive <file>debian/rules</file> script makes it
1797 impossible to auto-compile that package and also makes it
1798 hard for other people to reproduce the same binary
1799 package, all <em>required targets</em> must be
1800 non-interactive. At a minimum, required targets are the
1801 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1802 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1803 <em>binary-indep</em>, and <em>build</em>. It also follows
1804 that any target that these targets depend on must also be
1809 The targets are as follows (required unless stated otherwise):
1811 <tag><tt>build</tt></tag>
1814 The <tt>build</tt> target should perform all the
1815 configuration and compilation of the package.
1816 If a package has an interactive pre-build
1817 configuration routine, the Debian source package
1818 must either be built after this has taken place (so
1819 that the binary package can be built without rerunning
1820 the configuration) or the configuration routine
1821 modified to become non-interactive. (The latter is
1822 preferable if there are architecture-specific features
1823 detected by the configuration routine.)
1827 For some packages, notably ones where the same
1828 source tree is compiled in different ways to produce
1829 two binary packages, the <tt>build</tt> target
1830 does not make much sense. For these packages it is
1831 good enough to provide two (or more) targets
1832 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1833 for each of the ways of building the package, and a
1834 <tt>build</tt> target that does nothing. The
1835 <tt>binary</tt> target will have to build the
1836 package in each of the possible ways and make the
1837 binary package out of each.
1841 The <tt>build</tt> target must not do anything
1842 that might require root privilege.
1846 The <tt>build</tt> target may need to run the
1847 <tt>clean</tt> target first - see below.
1851 When a package has a configuration and build routine
1852 which takes a long time, or when the makefiles are
1853 poorly designed, or when <tt>build</tt> needs to
1854 run <tt>clean</tt> first, it is a good idea to
1855 <tt>touch build</tt> when the build process is
1856 complete. This will ensure that if <tt>debian/rules
1857 build</tt> is run again it will not rebuild the whole
1859 Another common way to do this is for <tt>build</tt>
1860 to depend on <prgn>build-stamp</prgn> and to do
1861 nothing else, and for the <prgn>build-stamp</prgn>
1862 target to do the building and to <tt>touch
1863 build-stamp</tt> on completion. This is
1864 especially useful if the build routine creates a
1865 file or directory called <tt>build</tt>; in such a
1866 case, <tt>build</tt> will need to be listed as
1867 a phony target (i.e., as a dependency of the
1868 <tt>.PHONY</tt> target). See the documentation of
1869 <prgn>make</prgn> for more information on phony
1875 <tag><tt>build-arch</tt> (optional),
1876 <tt>build-indep</tt> (optional)
1880 A package may also provide both of the targets
1881 <tt>build-arch</tt> and <tt>build-indep</tt>.
1882 The <tt>build-arch</tt> target, if provided, should
1883 perform all the configuration and compilation required for
1884 producing all architecture-dependant binary packages
1885 (those packages for which the body of the
1886 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1887 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1888 target, if provided, should perform all the configuration
1889 and compilation required for producing all
1890 architecture-independent binary packages (those packages
1891 for which the body of the <tt>Architecture</tt> field
1892 in <tt>debian/control</tt> is <tt>all</tt>).
1893 The <tt>build</tt> target should depend on those of the
1894 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1895 are provided in the rules file.<footnote>
1896 The intent of this split is so that binary-only builds
1897 need not install the dependencies required for
1898 the <tt>build-indep</tt> target. However, this is not
1899 yet used in practice since <tt>dpkg-buildpackage
1900 -B</tt>, and therefore the autobuilders,
1901 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1902 due to the difficulties in determining whether the
1903 optional <tt>build-arch</tt> target exists.
1908 If one or both of the targets <tt>build-arch</tt> and
1909 <tt>build-indep</tt> are not provided, then invoking
1910 <file>debian/rules</file> with one of the not-provided
1911 targets as arguments should produce a exit status code
1912 of 2. Usually this is provided automatically by make
1913 if the target is missing.
1917 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1918 must not do anything that might require root privilege.
1922 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1923 <tt>binary-indep</tt>
1927 The <tt>binary</tt> target must be all that is
1928 necessary for the user to build the binary package(s)
1929 produced from this source package. It is
1930 split into two parts: <prgn>binary-arch</prgn> builds
1931 the binary packages which are specific to a particular
1932 architecture, and <tt>binary-indep</tt> builds
1933 those which are not.
1936 <tt>binary</tt> may be (and commonly is) a target with
1937 no commands which simply depends on
1938 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1941 Both <tt>binary-*</tt> targets should depend on the
1942 <tt>build</tt> target, or on the appropriate
1943 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1944 provided, so that the package is built if it has not
1945 been already. It should then create the relevant
1946 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1947 make their control files and <prgn>dpkg-deb</prgn> to
1948 build them and place them in the parent of the top
1953 Both the <tt>binary-arch</tt> and
1954 <tt>binary-indep</tt> targets <em>must</em> exist.
1955 If one of them has nothing to do (which will always be
1956 the case if the source generates only a single binary
1957 package, whether architecture-dependent or not), it
1958 must still exist and must always succeed.
1962 The <tt>binary</tt> targets must be invoked as
1964 The <prgn>fakeroot</prgn> package often allows one
1965 to build a package correctly even without being
1971 <tag><tt>clean</tt></tag>
1974 This must undo any effects that the <tt>build</tt>
1975 and <tt>binary</tt> targets may have had, except
1976 that it should leave alone any output files created in
1977 the parent directory by a run of a <tt>binary</tt>
1982 If a <tt>build</tt> file is touched at the end of
1983 the <tt>build</tt> target, as suggested above, it
1984 should be removed as the first action that
1985 <tt>clean</tt> performs, so that running
1986 <tt>build</tt> again after an interrupted
1987 <tt>clean</tt> doesn't think that everything is
1992 The <tt>clean</tt> target may need to be
1993 invoked as root if <tt>binary</tt> has been
1994 invoked since the last <tt>clean</tt>, or if
1995 <tt>build</tt> has been invoked as root (since
1996 <tt>build</tt> may create directories, for
2001 <tag><tt>get-orig-source</tt> (optional)</tag>
2004 This target fetches the most recent version of the
2005 original source package from a canonical archive site
2006 (via FTP or WWW, for example), does any necessary
2007 rearrangement to turn it into the original source
2008 tar file format described below, and leaves it in the
2013 This target may be invoked in any directory, and
2014 should take care to clean up any temporary files it
2019 This target is optional, but providing it if
2020 possible is a good idea.
2024 <tag><tt>patch</tt> (optional)</tag>
2027 This target performs whatever additional actions are
2028 required to make the source ready for editing (unpacking
2029 additional upstream archives, applying patches, etc.).
2030 It is recommended to be implemented for any package where
2031 <tt>dpkg-source -x</tt> does not result in source ready
2032 for additional modification. See
2033 <ref id="readmesource">.
2039 The <tt>build</tt>, <tt>binary</tt> and
2040 <tt>clean</tt> targets must be invoked with the current
2041 directory being the package's top-level directory.
2046 Additional targets may exist in <file>debian/rules</file>,
2047 either as published or undocumented interfaces or for the
2048 package's internal use.
2052 The architectures we build on and build for are determined
2053 by <prgn>make</prgn> variables using the utility
2054 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2055 You can determine the
2056 Debian architecture and the GNU style architecture
2057 specification string for the build machine (the machine type
2058 we are building on) as well as for the host machine (the
2059 machine type we are building for). Here is a list of
2060 supported <prgn>make</prgn> variables:
2061 <list compact="compact">
2063 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2066 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2069 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2072 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2073 specification string)
2076 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2077 <tt>DEB_*_GNU_TYPE</tt>)
2080 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2081 <tt>DEB_*_GNU_TYPE</tt>)
2083 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2084 the build machine or <tt>HOST</tt> for specification of the
2089 Backward compatibility can be provided in the rules file
2090 by setting the needed variables to suitable default
2091 values; please refer to the documentation of
2092 <prgn>dpkg-architecture</prgn> for details.
2096 It is important to understand that the <tt>DEB_*_ARCH</tt>
2097 string only determines which Debian architecture we are
2098 building on or for. It should not be used to get the CPU
2099 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2100 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2101 GNU style variables should generally only be used with upstream
2105 <sect1 id="debianrules-options">
2106 <heading><file>debian/rules</file> and
2107 <tt>DEB_BUILD_OPTIONS</tt></heading>
2110 Supporting the standardized environment variable
2111 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2112 contain several flags to change how a package is compiled and
2113 built. Each flag must be in the form <var>flag</var> or
2114 <var>flag</var>=<var>options</var>. If multiple flags are
2115 given, they must be separated by whitespace.<footnote>
2116 Some packages support any delimiter, but whitespace is the
2117 easiest to parse inside a makefile and avoids ambiguity with
2118 flag values that contain commas.
2120 <var>flag</var> must start with a lowercase letter
2121 (<tt>a-z</tt>) and consist only of lowercase letters,
2122 numbers (<tt>0-9</tt>), and the characters
2123 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2124 <var>options</var> must not contain whitespace. The same
2125 tag should not be given multiple times with conflicting
2126 values. Package maintainers may assume that
2127 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2131 The meaning of the following tags has been standardized:
2135 This tag says to not run any build-time test suite
2136 provided by the package.
2140 The presence of this tag means that the package should
2141 be compiled with a minimum of optimization. For C
2142 programs, it is best to add <tt>-O0</tt> to
2143 <tt>CFLAGS</tt> (although this is usually the default).
2144 Some programs might fail to build or run at this level
2145 of optimization; it may be necessary to use
2146 <tt>-O1</tt>, for example.
2150 This tag means that the debugging symbols should not be
2151 stripped from the binary during installation, so that
2152 debugging information may be included in the package.
2154 <tag>parallel=n</tag>
2156 This tag means that the package should be built using up
2157 to <tt>n</tt> parallel processes if the package build
2158 system supports this.<footnote>
2159 Packages built with <tt>make</tt> can often implement
2160 this by passing the <tt>-j</tt><var>n</var> option to
2163 If the package build system does not support parallel
2164 builds, this string must be ignored. If the package
2165 build system only supports a lower level of concurrency
2166 than <var>n</var>, the package should be built using as
2167 many parallel processes as the package build system
2168 supports. It is up to the package maintainer to decide
2169 whether the package build times are long enough and the
2170 package build system is robust enough to make supporting
2171 parallel builds worthwhile.
2177 Unknown flags must be ignored by <file>debian/rules</file>.
2181 The following makefile snippet is an example of how one may
2182 implement the build options; you will probably have to
2183 massage this example in order to make it work for your
2185 <example compact="compact">
2188 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2189 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2190 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2191 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2193 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2198 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2199 INSTALL_PROGRAM += -s
2201 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2202 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2203 MAKEFLAGS += -j$(NUMJOBS)
2208 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2209 # Code to run the package test suite.
2216 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2217 <sect id="substvars">
2218 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2221 When <prgn>dpkg-gencontrol</prgn>,
2222 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2223 generate control files, they perform variable substitutions
2224 on their output just before writing it. Variable
2225 substitutions have the form <tt>${<var>variable</var>}</tt>.
2226 The optional file <file>debian/substvars</file> contains
2227 variable substitutions to be used; variables can also be set
2228 directly from <file>debian/rules</file> using the <tt>-V</tt>
2229 option to the source packaging commands, and certain
2230 predefined variables are also available.
2234 The <file>debian/substvars</file> file is usually generated and
2235 modified dynamically by <file>debian/rules</file> targets, in
2236 which case it must be removed by the <tt>clean</tt> target.
2240 See <manref name="deb-substvars" section="5"> for full
2241 details about source variable substitutions, including the
2242 format of <file>debian/substvars</file>.</p>
2245 <sect id="debianwatch">
2246 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2249 This is an optional, recommended configuration file for the
2250 <tt>uscan</tt> utility which defines how to automatically scan
2251 ftp or http sites for newly available updates of the
2252 package. This is used
2253 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2254 tools to help with quality control and maintenance of the
2255 distribution as a whole.
2260 <sect id="debianfiles">
2261 <heading>Generated files list: <file>debian/files</file></heading>
2264 This file is not a permanent part of the source tree; it
2265 is used while building packages to record which files are
2266 being generated. <prgn>dpkg-genchanges</prgn> uses it
2267 when it generates a <file>.changes</file> file.
2271 It should not exist in a shipped source package, and so it
2272 (and any backup files or temporary files such as
2273 <file>files.new</file><footnote>
2274 <file>files.new</file> is used as a temporary file by
2275 <prgn>dpkg-gencontrol</prgn> and
2276 <prgn>dpkg-distaddfile</prgn> - they write a new
2277 version of <tt>files</tt> here before renaming it,
2278 to avoid leaving a corrupted copy if an error
2280 </footnote>) should be removed by the
2281 <tt>clean</tt> target. It may also be wise to
2282 ensure a fresh start by emptying or removing it at the
2283 start of the <tt>binary</tt> target.
2287 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2288 package, it adds an entry to <file>debian/files</file> for the
2289 <file>.deb</file> file that will be created when <tt>dpkg-deb
2290 --build</tt> is run for that binary package. So for most
2291 packages all that needs to be done with this file is to
2292 delete it in the <tt>clean</tt> target.
2296 If a package upload includes files besides the source
2297 package and any binary packages whose control files were
2298 made with <prgn>dpkg-gencontrol</prgn> then they should be
2299 placed in the parent of the package's top-level directory
2300 and <prgn>dpkg-distaddfile</prgn> should be called to add
2301 the file to the list in <file>debian/files</file>.</p>
2304 <sect id="embeddedfiles">
2305 <heading>Convenience copies of code</heading>
2308 Some software packages include in their distribution convenience
2309 copies of code from other software packages, generally so that
2310 users compiling from source don't have to download multiple
2311 packages. Debian packages should not make use of these
2312 convenience copies unless the included package is explicitly
2313 intended to be used in this way.<footnote>
2314 For example, parts of the GNU build system work like this.
2316 If the included code is already in the Debian archive in the
2317 form of a library, the Debian packaging should ensure that
2318 binary packages reference the libraries already in Debian and
2319 the convenience copy is not used. If the included code is not
2320 already in Debian, it should be packaged separately as a
2321 prerequisite if possible.
2323 Having multiple copies of the same code in Debian is
2324 inefficient, often creates either static linking or shared
2325 library conflicts, and, most importantly, increases the
2326 difficulty of handling security vulnerabilities in the
2332 <sect id="readmesource">
2333 <heading>Source package handling:
2334 <file>debian/README.source</file></heading>
2337 If running <prgn>dpkg-source -x</prgn> on a source package
2338 doesn't produce the source of the package, ready for editing,
2339 and allow one to make changes and run
2340 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2341 without taking any additional steps, creating a
2342 <file>debian/README.source</file> documentation file is
2343 recommended. This file should explain how to do all of the
2346 <item>Generate the fully patched source, in a form ready for
2347 editing, that would be built to create Debian
2348 packages. Doing this with a <tt>patch</tt> target in
2349 <file>debian/rules</file> is recommended; see
2350 <ref id="debianrules">.</item>
2351 <item>Modify the source and save those modifications so that
2352 they will be applied when building the package.</item>
2353 <item>Remove source modifications that are currently being
2354 applied when building the package.</item>
2355 <item>Optionally, document what steps are necessary to
2356 upgrade the Debian source package to a new upstream version,
2357 if applicable.</item>
2359 This explanation should include specific commands and mention
2360 any additional required Debian packages. It should not assume
2361 familiarity with any specific Debian packaging system or patch
2366 This explanation may refer to a documentation file installed by
2367 one of the package's build dependencies provided that the
2368 referenced documentation clearly explains these tasks and is not
2369 a general reference manual.
2373 <file>debian/README.source</file> may also include any other
2374 information that would be helpful to someone modifying the
2375 source package. Even if the package doesn't fit the above
2376 description, maintainers are encouraged to document in a
2377 <file>debian/README.source</file> file any source package with a
2378 particularly complex or unintuitive source layout or build
2379 system (for example, a package that builds the same source
2380 multiple times to generate different binary packages).
2386 <chapt id="controlfields">
2387 <heading>Control files and their fields</heading>
2390 The package management system manipulates data represented in
2391 a common format, known as <em>control data</em>, stored in
2392 <em>control files</em>.
2393 Control files are used for source packages, binary packages and
2394 the <file>.changes</file> files which control the installation
2395 of uploaded files<footnote>
2396 <prgn>dpkg</prgn>'s internal databases are in a similar
2401 <sect id="controlsyntax">
2402 <heading>Syntax of control files</heading>
2405 A control file consists of one or more paragraphs of
2407 The paragraphs are also sometimes referred to as stanzas.
2409 The paragraphs are separated by blank lines. Some control
2410 files allow only one paragraph; others allow several, in
2411 which case each paragraph usually refers to a different
2412 package. (For example, in source packages, the first
2413 paragraph refers to the source package, and later paragraphs
2414 refer to binary packages generated from the source.)
2418 Each paragraph consists of a series of data fields; each
2419 field consists of the field name, followed by a colon and
2420 then the data/value associated with that field. It ends at
2421 the end of the (logical) line. Horizontal whitespace
2422 (spaces and tabs) may occur immediately before or after the
2423 value and is ignored there; it is conventional to put a
2424 single space after the colon. For example, a field might
2426 <example compact="compact">
2429 the field name is <tt>Package</tt> and the field value
2434 A paragraph must not contain more than one instance of a
2435 particular field name.
2439 Many fields' values may span several lines; in this case
2440 each continuation line must start with a space or a tab.
2441 Any trailing spaces or tabs at the end of individual
2442 lines of a field value are ignored.
2446 In fields where it is specified that lines may not wrap,
2447 only a single line of data is allowed and whitespace is not
2448 significant in a field body. Whitespace must not appear
2449 inside names (of packages, architectures, files or anything
2450 else) or version numbers, or between the characters of
2451 multi-character version relationships.
2455 Field names are not case-sensitive, but it is usual to
2456 capitalize the field names using mixed case as shown below.
2457 Field values are case-sensitive unless the description of the
2458 field says otherwise.
2462 Blank lines, or lines consisting only of spaces and tabs,
2463 are not allowed within field values or between fields - that
2464 would mean a new paragraph.
2468 All control files must be encoded in UTF-8.
2472 <sect id="sourcecontrolfiles">
2473 <heading>Source package control files -- <file>debian/control</file></heading>
2476 The <file>debian/control</file> file contains the most vital
2477 (and version-independent) information about the source package
2478 and about the binary packages it creates.
2482 The first paragraph of the control file contains information about
2483 the source package in general. The subsequent sets each describe a
2484 binary package that the source tree builds.
2488 The fields in the general paragraph (the first one, for the source
2491 <list compact="compact">
2492 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2493 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2495 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2496 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2497 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2498 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2499 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2504 The fields in the binary package paragraphs are:
2506 <list compact="compact">
2507 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2508 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2509 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2510 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2511 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2512 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2513 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2514 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2519 The syntax and semantics of the fields are described below.
2523 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2524 generate control files for binary packages (see below), by
2525 <prgn>dpkg-genchanges</prgn> to generate the
2526 <file>.changes</file> file to accompany the upload, and by
2527 <prgn>dpkg-source</prgn> when it creates the
2528 <file>.dsc</file> source control file as part of a source
2529 archive. Many fields are permitted to span multiple lines in
2530 <file>debian/control</file> but not in any other control
2531 file. These tools are responsible for removing the line
2532 breaks from such fields when using fields from
2533 <file>debian/control</file> to generate other control files.
2537 The fields here may contain variable references - their
2538 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2539 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2540 when they generate output control files.
2541 See <ref id="substvars"> for details.
2545 In addition to the control file syntax described <qref
2546 id="controlsyntax">above</qref>, this file may also contain
2547 comment lines starting with <tt>#</tt> without any preceding
2548 whitespace. All such lines are ignored, even in the middle of
2549 continuation lines for a multiline field, and do not end a
2555 <sect id="binarycontrolfiles">
2556 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2559 The <file>DEBIAN/control</file> file contains the most vital
2560 (and version-dependent) information about a binary package. It
2561 consists of a single paragraph.
2565 The fields in this file are:
2567 <list compact="compact">
2568 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2569 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2570 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2571 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2572 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2573 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2575 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2576 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2577 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2579 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2584 <sect id="debiansourcecontrolfiles">
2585 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2588 This file consists of a single paragraph, possibly surrounded by
2589 a PGP signature. The fields of that paragraph are listed below.
2590 Their syntax is described above, in <ref id="pkg-controlfields">.
2592 <list compact="compact">
2593 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2594 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2595 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2596 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2597 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2598 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2599 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2600 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2601 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2602 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2603 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2604 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2605 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2610 The source package control file is generated by
2611 <prgn>dpkg-source</prgn> when it builds the source
2612 archive, from other files in the source package,
2613 described above. When unpacking, it is checked against
2614 the files and directories in the other parts of the
2620 <sect id="debianchangesfiles">
2621 <heading>Debian changes files -- <file>.changes</file></heading>
2624 The <file>.changes</file> files are used by the Debian archive
2625 maintenance software to process updates to packages. They
2626 consist of a single paragraph, possibly surrounded by a PGP
2627 signature. That paragraph contains information from the
2628 <file>debian/control</file> file and other data about the
2629 source package gathered via <file>debian/changelog</file>
2630 and <file>debian/rules</file>.
2634 <file>.changes</file> files have a format version that is
2635 incremented whenever the documented fields or their meaning
2636 change. This document describes format &changesversion;.
2640 The fields in this file are:
2642 <list compact="compact">
2643 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2644 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2645 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2646 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2647 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2651 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2653 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2655 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2657 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2658 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2663 <sect id="controlfieldslist">
2664 <heading>List of fields</heading>
2666 <sect1 id="f-Source">
2667 <heading><tt>Source</tt></heading>
2670 This field identifies the source package name.
2674 In <file>debian/control</file> or a <file>.dsc</file> file,
2675 this field must contain only the name of the source package.
2679 In a binary package control file or a <file>.changes</file>
2680 file, the source package name may be followed by a version
2681 number in parentheses<footnote>
2682 It is customary to leave a space after the package name
2683 if a version number is specified.
2685 This version number may be omitted (and is, by
2686 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2687 the <tt>Version</tt> field of the binary package in
2688 question. The field itself may be omitted from a binary
2689 package control file when the source package has the same
2690 name and version as the binary package.
2694 Package names (both source and binary,
2695 see <ref id="f-Package">) must consist only of lower case
2696 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2697 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2698 (<tt>.</tt>). They must be at least two characters long and
2699 must start with an alphanumeric character.
2703 <sect1 id="f-Maintainer">
2704 <heading><tt>Maintainer</tt></heading>
2707 The package maintainer's name and email address. The name
2708 must come first, then the email address inside angle
2709 brackets <tt><></tt> (in RFC822 format).
2713 If the maintainer's name contains a full stop then the
2714 whole field will not work directly as an email address due
2715 to a misfeature in the syntax specified in RFC822; a
2716 program using this field as an address must check for this
2717 and correct the problem if necessary (for example by
2718 putting the name in round brackets and moving it to the
2719 end, and bringing the email address forward).
2723 <sect1 id="f-Uploaders">
2724 <heading><tt>Uploaders</tt></heading>
2727 List of the names and email addresses of co-maintainers of
2728 the package, if any. If the package has other maintainers
2729 beside the one named in the
2730 <qref id="f-Maintainer">Maintainer field</qref>, their names
2731 and email addresses should be listed here. The format of each
2732 entry is the same as that of the Maintainer field, and
2733 multiple entries must be comma separated. This is an optional
2738 Any parser that interprets the Uploaders field in
2739 <file>debian/control</file> must permit it to span multiple
2740 lines. Line breaks in an Uploaders field that spans multiple
2741 lines are not significant and the semantics of the field are
2742 the same as if the line breaks had not been present.
2746 <sect1 id="f-Changed-By">
2747 <heading><tt>Changed-By</tt></heading>
2750 The name and email address of the person who prepared this
2751 version of the package, usually a maintainer. The syntax is
2752 the same as for the <qref id="f-Maintainer">Maintainer
2757 <sect1 id="f-Section">
2758 <heading><tt>Section</tt></heading>
2761 This field specifies an application area into which the package
2762 has been classified. See <ref id="subsections">.
2766 When it appears in the <file>debian/control</file> file,
2767 it gives the value for the subfield of the same name in
2768 the <tt>Files</tt> field of the <file>.changes</file> file.
2769 It also gives the default for the same field in the binary
2774 <sect1 id="f-Priority">
2775 <heading><tt>Priority</tt></heading>
2778 This field represents how important it is that the user
2779 have the package installed. See <ref id="priorities">.
2783 When it appears in the <file>debian/control</file> file,
2784 it gives the value for the subfield of the same name in
2785 the <tt>Files</tt> field of the <file>.changes</file> file.
2786 It also gives the default for the same field in the binary
2791 <sect1 id="f-Package">
2792 <heading><tt>Package</tt></heading>
2795 The name of the binary package.
2799 Binary package names must follow the same syntax and
2800 restrictions as source package names. See <ref id="f-Source">
2805 <sect1 id="f-Architecture">
2806 <heading><tt>Architecture</tt></heading>
2809 Depending on context and the control file used, the
2810 <tt>Architecture</tt> field can include the following sets of
2814 A unique single word identifying a Debian machine
2815 architecture as described in <ref id="arch-spec">.
2818 An architecture wildcard identifying a set of Debian
2819 machine architectures, see <ref id="arch-wildcard-spec">.
2820 <tt>any</tt> matches all Debian machine architectures
2821 and is the most frequently used.
2824 <tt>all</tt>, which indicates an
2825 architecture-independent package.
2828 <tt>source</tt>, which indicates a source package.
2834 In the main <file>debian/control</file> file in the source
2835 package, this field may contain the special
2836 value <tt>all</tt>, the special architecture
2837 wildcard <tt>any</tt>, or a list of specific and wildcard
2838 architectures separated by spaces. If <tt>all</tt>
2839 or <tt>any</tt> appears, that value must be the entire
2840 contents of the field. Most packages will use
2841 either <tt>all</tt> or <tt>any</tt>.
2845 Specifying a specific list of architectures indicates that the
2846 source will build an architecture-dependent package only on
2847 architectures included in the list. Specifying a list of
2848 architecture wildcards indicates that the source will build an
2849 architecture-dependent package on only those architectures
2850 that match any of the specified architecture wildcards.
2851 Specifying a list of architectures or architecture wildcards
2852 other than <tt>any</tt> is for the minority of cases where a
2853 program is not portable or is not useful on some
2854 architectures. Where possible, the program should be made
2859 In the source package control file <file>.dsc</file>, this
2860 field may contain either the architecture
2861 wildcard <tt>any</tt> or a list of architectures and
2862 architecture wildcards separated by spaces. If a list is
2863 given, it may include (or consist solely of) the special
2864 value <tt>all</tt>. In other words, in <file>.dsc</file>
2865 files unlike the <file>debian/control</file>, <tt>all</tt> may
2866 occur in combination with specific architectures.
2867 The <tt>Architecture</tt> field in the source package control
2868 file <file>.dsc</file> is generally constructed from
2869 the <tt>Architecture</tt> fields in
2870 the <file>debian/control</file> in the source package.
2874 Specifying <tt>any</tt> indicates that the source package
2875 isn't dependent on any particular architecture and should
2876 compile fine on any one. The produced binary package(s)
2877 will either be specific to whatever the current build
2878 architecture is or will be architecture-independent.
2882 Specifying only <tt>all</tt> indicates that the source package
2883 will only build architecture-independent packages. If this is
2884 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2885 <tt>any</tt> implies that the source package will build at
2886 least one architecture-dependent package.
2890 Specifying a list of architectures or architecture wildcards
2891 indicates that the source will build an architecture-dependent
2892 package, and will only work correctly on the listed or
2893 matching architectures. If the source package also builds at
2894 least one architecture-independent package, <tt>all</tt> will
2895 also be included in the list.
2899 In a <file>.changes</file> file, the <tt>Architecture</tt>
2900 field lists the architecture(s) of the package(s) currently
2901 being uploaded. This will be a list; if the source for the
2902 package is also being uploaded, the special
2903 entry <tt>source</tt> is also present. <tt>all</tt> will be
2904 present if any architecture-independent packages are being
2905 uploaded. Architecture wildcards such as <tt>any</tt> must
2906 never occur in the <tt>Architecture</tt> field in
2907 the <file>.changes</file> file.
2911 See <ref id="debianrules"> for information on how to get
2912 the architecture for the build process.
2916 <sect1 id="f-Essential">
2917 <heading><tt>Essential</tt></heading>
2920 This is a boolean field which may occur only in the
2921 control file of a binary package or in a per-package fields
2922 paragraph of a main source control data file.
2926 If set to <tt>yes</tt> then the package management system
2927 will refuse to remove the package (upgrading and replacing
2928 it is still possible). The other possible value is <tt>no</tt>,
2929 which is the same as not having the field at all.
2934 <heading>Package interrelationship fields:
2935 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2936 <tt>Recommends</tt>, <tt>Suggests</tt>,
2937 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2938 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2942 These fields describe the package's relationships with
2943 other packages. Their syntax and semantics are described
2944 in <ref id="relationships">.</p>
2947 <sect1 id="f-Standards-Version">
2948 <heading><tt>Standards-Version</tt></heading>
2951 The most recent version of the standards (the policy
2952 manual and associated texts) with which the package
2957 The version number has four components: major and minor
2958 version number and major and minor patch level. When the
2959 standards change in a way that requires every package to
2960 change the major number will be changed. Significant
2961 changes that will require work in many packages will be
2962 signaled by a change to the minor number. The major patch
2963 level will be changed for any change to the meaning of the
2964 standards, however small; the minor patch level will be
2965 changed when only cosmetic, typographical or other edits
2966 are made which neither change the meaning of the document
2967 nor affect the contents of packages.
2971 Thus only the first three components of the policy version
2972 are significant in the <em>Standards-Version</em> control
2973 field, and so either these three components or all four
2974 components may be specified.<footnote>
2975 In the past, people specified the full version number
2976 in the Standards-Version field, for example "2.3.0.0".
2977 Since minor patch-level changes don't introduce new
2978 policy, it was thought it would be better to relax
2979 policy and only require the first 3 components to be
2980 specified, in this example "2.3.0". All four
2981 components may still be used if someone wishes to do so.
2987 <sect1 id="f-Version">
2988 <heading><tt>Version</tt></heading>
2991 The version number of a package. The format is:
2992 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2996 The three components here are:
2998 <tag><var>epoch</var></tag>
3001 This is a single (generally small) unsigned integer. It
3002 may be omitted, in which case zero is assumed. If it is
3003 omitted then the <var>upstream_version</var> may not
3008 It is provided to allow mistakes in the version numbers
3009 of older versions of a package, and also a package's
3010 previous version numbering schemes, to be left behind.
3014 <tag><var>upstream_version</var></tag>
3017 This is the main part of the version number. It is
3018 usually the version number of the original ("upstream")
3019 package from which the <file>.deb</file> file has been made,
3020 if this is applicable. Usually this will be in the same
3021 format as that specified by the upstream author(s);
3022 however, it may need to be reformatted to fit into the
3023 package management system's format and comparison
3028 The comparison behavior of the package management system
3029 with respect to the <var>upstream_version</var> is
3030 described below. The <var>upstream_version</var>
3031 portion of the version number is mandatory.
3035 The <var>upstream_version</var> may contain only
3036 alphanumerics<footnote>
3037 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3039 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3040 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3041 tilde) and should start with a digit. If there is no
3042 <var>debian_revision</var> then hyphens are not allowed;
3043 if there is no <var>epoch</var> then colons are not
3048 <tag><var>debian_revision</var></tag>
3051 This part of the version number specifies the version of
3052 the Debian package based on the upstream version. It
3053 may contain only alphanumerics and the characters
3054 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3055 tilde) and is compared in the same way as the
3056 <var>upstream_version</var> is.
3060 It is optional; if it isn't present then the
3061 <var>upstream_version</var> may not contain a hyphen.
3062 This format represents the case where a piece of
3063 software was written specifically to be a Debian
3064 package, where the Debian package source must always
3065 be identical to the pristine source and therefore no
3066 revision indication is required.
3070 It is conventional to restart the
3071 <var>debian_revision</var> at <tt>1</tt> each time the
3072 <var>upstream_version</var> is increased.
3076 The package management system will break the version
3077 number apart at the last hyphen in the string (if there
3078 is one) to determine the <var>upstream_version</var> and
3079 <var>debian_revision</var>. The absence of a
3080 <var>debian_revision</var> is equivalent to a
3081 <var>debian_revision</var> of <tt>0</tt>.
3088 When comparing two version numbers, first the <var>epoch</var>
3089 of each are compared, then the <var>upstream_version</var> if
3090 <var>epoch</var> is equal, and then <var>debian_revision</var>
3091 if <var>upstream_version</var> is also equal.
3092 <var>epoch</var> is compared numerically. The
3093 <var>upstream_version</var> and <var>debian_revision</var>
3094 parts are compared by the package management system using the
3095 following algorithm:
3099 The strings are compared from left to right.
3103 First the initial part of each string consisting entirely of
3104 non-digit characters is determined. These two parts (one of
3105 which may be empty) are compared lexically. If a difference
3106 is found it is returned. The lexical comparison is a
3107 comparison of ASCII values modified so that all the letters
3108 sort earlier than all the non-letters and so that a tilde
3109 sorts before anything, even the end of a part. For example,
3110 the following parts are in sorted order from earliest to
3111 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3112 <tt>a</tt>.<footnote>
3113 One common use of <tt>~</tt> is for upstream pre-releases.
3114 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3115 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3120 Then the initial part of the remainder of each string which
3121 consists entirely of digit characters is determined. The
3122 numerical values of these two parts are compared, and any
3123 difference found is returned as the result of the comparison.
3124 For these purposes an empty string (which can only occur at
3125 the end of one or both version strings being compared) counts
3130 These two steps (comparing and removing initial non-digit
3131 strings and initial digit strings) are repeated until a
3132 difference is found or both strings are exhausted.
3136 Note that the purpose of epochs is to allow us to leave behind
3137 mistakes in version numbering, and to cope with situations
3138 where the version numbering scheme changes. It is
3139 <em>not</em> intended to cope with version numbers containing
3140 strings of letters which the package management system cannot
3141 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3142 silly orderings.<footnote>
3143 The author of this manual has heard of a package whose
3144 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3145 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3151 <sect1 id="f-Description">
3152 <heading><tt>Description</tt></heading>
3155 In a source or binary control file, the <tt>Description</tt>
3156 field contains a description of the binary package, consisting
3157 of two parts, the synopsis or the short description, and the
3158 long description. The field's format is as follows:
3163 Description: <single line synopsis>
3164 <extended description over several lines>
3169 The lines in the extended description can have these formats:
3175 Those starting with a single space are part of a paragraph.
3176 Successive lines of this form will be word-wrapped when
3177 displayed. The leading space will usually be stripped off.
3181 Those starting with two or more spaces. These will be
3182 displayed verbatim. If the display cannot be panned
3183 horizontally, the displaying program will line wrap them "hard"
3184 (i.e., without taking account of word breaks). If it can they
3185 will be allowed to trail off to the right. None, one or two
3186 initial spaces may be deleted, but the number of spaces
3187 deleted from each line will be the same (so that you can have
3188 indenting work correctly, for example).
3192 Those containing a single space followed by a single full stop
3193 character. These are rendered as blank lines. This is the
3194 <em>only</em> way to get a blank line<footnote>
3195 Completely empty lines will not be rendered as blank lines.
3196 Instead, they will cause the parser to think you're starting
3197 a whole new record in the control file, and will therefore
3198 likely abort with an error.
3203 Those containing a space, a full stop and some more characters.
3204 These are for future expansion. Do not use them.
3210 Do not use tab characters. Their effect is not predictable.
3214 See <ref id="descriptions"> for further information on this.
3218 In a <file>.changes</file> file, the <tt>Description</tt>
3219 field contains a summary of the descriptions for the packages
3220 being uploaded. For this case, the first line of the field
3221 value (the part on the same line as <tt>Description:</tt>) is
3222 always empty. The content of the field is expressed as
3223 continuation lines, one line per package. Each line is
3224 indented by one space and contains the name of a binary
3225 package, a space, a hyphen (<tt>-</tt>), a space, and the
3226 short description line from that package.
3230 <sect1 id="f-Distribution">
3231 <heading><tt>Distribution</tt></heading>
3234 In a <file>.changes</file> file or parsed changelog output
3235 this contains the (space-separated) name(s) of the
3236 distribution(s) where this version of the package should
3237 be installed. Valid distributions are determined by the
3238 archive maintainers.<footnote>
3239 Example distribution names in the Debian archive used in
3240 <file>.changes</file> files are:
3241 <taglist compact="compact">
3242 <tag><em>unstable</em></tag>
3244 This distribution value refers to the
3245 <em>developmental</em> part of the Debian distribution
3246 tree. Most new packages, new upstream versions of
3247 packages and bug fixes go into the <em>unstable</em>
3251 <tag><em>experimental</em></tag>
3253 The packages with this distribution value are deemed
3254 by their maintainers to be high risk. Oftentimes they
3255 represent early beta or developmental packages from
3256 various sources that the maintainers want people to
3257 try, but are not ready to be a part of the other parts
3258 of the Debian distribution tree.
3263 Others are used for updating stable releases or for
3264 security uploads. More information is available in the
3265 Debian Developer's Reference, section "The Debian
3269 The Debian archive software only supports listing a single
3270 distribution. Migration of packages to other distributions is
3271 handled outside of the upload process.
3276 <heading><tt>Date</tt></heading>
3279 This field includes the date the package was built or last
3280 edited. It must be in the same format as the <var>date</var>
3281 in a <file>debian/changelog</file> entry.
3285 The value of this field is usually extracted from the
3286 <file>debian/changelog</file> file - see
3287 <ref id="dpkgchangelog">).
3291 <sect1 id="f-Format">
3292 <heading><tt>Format</tt></heading>
3295 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3296 files, this field declares the format version of that file.
3297 The syntax of the field value is the same as that of
3298 a <qref id="f-Version">package version number</qref> except
3299 that no epoch or Debian revision is allowed. The format
3300 described in this document is <tt>&changesversion;</tt>.
3304 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3305 Debian source control</qref> files, this field declares the
3306 format of the source package. The field value is used by
3307 programs acting on a source package to interpret the list of
3308 files in the source package and determine how to unpack it.
3309 The syntax of the field value is a numeric major revision, a
3310 period, a numeric minor revision, and then an optional subtype
3311 after whitespace, which if specified is an alphanumeric word
3312 in parentheses. The subtype is optional in the syntax but may
3313 be mandatory for particular source format revisions.
3315 The source formats currently supported by the Debian archive
3316 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3317 and <tt>3.0 (quilt)</tt>.
3322 <sect1 id="f-Urgency">
3323 <heading><tt>Urgency</tt></heading>
3326 This is a description of how important it is to upgrade to
3327 this version from previous ones. It consists of a single
3328 keyword taking one of the values <tt>low</tt>,
3329 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3330 <tt>critical</tt><footnote>
3331 Other urgency values are supported with configuration
3332 changes in the archive software but are not used in Debian.
3333 The urgency affects how quickly a package will be considered
3334 for inclusion into the <tt>testing</tt> distribution and
3335 gives an indication of the importance of any fixes included
3336 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3337 treated as synonymous.
3338 </footnote> (not case-sensitive) followed by an optional
3339 commentary (separated by a space) which is usually in
3340 parentheses. For example:
3343 Urgency: low (HIGH for users of diversions)
3349 The value of this field is usually extracted from the
3350 <file>debian/changelog</file> file - see
3351 <ref id="dpkgchangelog">.
3355 <sect1 id="f-Changes">
3356 <heading><tt>Changes</tt></heading>
3359 This field contains the human-readable changes data, describing
3360 the differences between the last version and the current one.
3364 The first line of the field value (the part on the same line
3365 as <tt>Changes:</tt>) is always empty. The content of the
3366 field is expressed as continuation lines, with each line
3367 indented by at least one space. Blank lines must be
3368 represented by a line consisting only of a space and a full
3373 The value of this field is usually extracted from the
3374 <file>debian/changelog</file> file - see
3375 <ref id="dpkgchangelog">).
3379 Each version's change information should be preceded by a
3380 "title" line giving at least the version, distribution(s)
3381 and urgency, in a human-readable way.
3385 If data from several versions is being returned the entry
3386 for the most recent version should be returned first, and
3387 entries should be separated by the representation of a
3388 blank line (the "title" line may also be followed by the
3389 representation of a blank line).
3393 <sect1 id="f-Binary">
3394 <heading><tt>Binary</tt></heading>
3397 This field is a list of binary packages. Its syntax and
3398 meaning varies depending on the control file in which it
3403 When it appears in the <file>.dsc</file> file, it lists binary
3404 packages which a source package can produce, separated by
3406 A space after each comma is conventional.
3407 </footnote>. It may span multiple lines. The source package
3408 does not necessarily produce all of these binary packages for
3409 every architecture. The source control file doesn't contain
3410 details of which architectures are appropriate for which of
3411 the binary packages.
3415 When it appears in a <file>.changes</file> file, it lists the
3416 names of the binary packages being uploaded, separated by
3417 whitespace (not commas). It may span multiple lines.
3421 <sect1 id="f-Installed-Size">
3422 <heading><tt>Installed-Size</tt></heading>
3425 This field appears in the control files of binary packages,
3426 and in the <file>Packages</file> files. It gives an estimate
3427 of the total amount of disk space required to install the
3428 named package. Actual installed size may vary based on block
3429 size, file system properties, or actions taken by package
3434 The disk space is given as the integer value of the estimated
3435 installed size in bytes, divided by 1024 and rounded up.
3439 <sect1 id="f-Files">
3440 <heading><tt>Files</tt></heading>
3443 This field contains a list of files with information about
3444 each one. The exact information and syntax varies with
3449 In all cases, Files is a multiline field. The first line of
3450 the field value (the part on the same line as <tt>Files:</tt>)
3451 is always empty. The content of the field is expressed as
3452 continuation lines, one line per file. Each line must be
3453 indented by one space and contain a number of sub-fields,
3454 separated by spaces, as described below.
3458 In the <file>.dsc</file> file, each line contains the MD5
3459 checksum, size and filename of the tar file and (if
3460 applicable) diff file which make up the remainder of the
3461 source package<footnote>
3462 That is, the parts which are not the <tt>.dsc</tt>.
3463 </footnote>. For example:
3466 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3467 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3469 The exact forms of the filenames are described
3470 in <ref id="pkg-sourcearchives">.
3474 In the <file>.changes</file> file this contains one line per
3475 file being uploaded. Each line contains the MD5 checksum,
3476 size, section and priority and the filename. For example:
3479 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3480 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3481 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3482 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3484 The <qref id="f-Section">section</qref>
3485 and <qref id="f-Priority">priority</qref> are the values of
3486 the corresponding fields in the main source control file. If
3487 no section or priority is specified then <tt>-</tt> should be
3488 used, though section and priority values must be specified for
3489 new packages to be installed properly.
3493 The special value <tt>byhand</tt> for the section in a
3494 <tt>.changes</tt> file indicates that the file in question
3495 is not an ordinary package file and must by installed by
3496 hand by the distribution maintainers. If the section is
3497 <tt>byhand</tt> the priority should be <tt>-</tt>.
3501 If a new Debian revision of a package is being shipped and
3502 no new original source archive is being distributed the
3503 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3504 entry for the original source archive
3505 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3506 but the <file>.changes</file> file should leave it out. In
3507 this case the original source archive on the distribution
3508 site must match exactly, byte-for-byte, the original
3509 source archive which was used to generate the
3510 <file>.dsc</file> file and diff which are being uploaded.</p>
3513 <sect1 id="f-Closes">
3514 <heading><tt>Closes</tt></heading>
3517 A space-separated list of bug report numbers that the upload
3518 governed by the .changes file closes.
3522 <sect1 id="f-Homepage">
3523 <heading><tt>Homepage</tt></heading>
3526 The URL of the web site for this package, preferably (when
3527 applicable) the site from which the original source can be
3528 obtained and any additional upstream documentation or
3529 information may be found. The content of this field is a
3530 simple URL without any surrounding characters such as
3535 <sect1 id="f-Checksums">
3536 <heading><tt>Checksums-Sha1</tt>
3537 and <tt>Checksums-Sha256</tt></heading>
3540 These fields contain a list of files with a checksum and size
3541 for each one. Both <tt>Checksums-Sha1</tt>
3542 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3543 only in the checksum algorithm used: SHA-1
3544 for <tt>Checksums-Sha1</tt> and SHA-256
3545 for <tt>Checksums-Sha256</tt>.
3549 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3550 multiline fields. The first line of the field value (the part
3551 on the same line as <tt>Checksums-Sha1:</tt>
3552 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3553 of the field is expressed as continuation lines, one line per
3554 file. Each line consists of the checksum, a space, the file
3555 size, a space, and the file name. For example (from
3556 a <file>.changes</file> file):
3559 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3560 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3561 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3562 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3564 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3565 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3566 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3567 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3572 In the <file>.dsc</file> file, these fields should list all
3573 files that make up the source package. In
3574 the <file>.changes</file> file, these fields should list all
3575 files being uploaded. The list of files in these fields
3576 must match the list of files in the <tt>Files</tt> field.
3582 <heading>User-defined fields</heading>
3585 Additional user-defined fields may be added to the
3586 source package control file. Such fields will be
3587 ignored, and not copied to (for example) binary or
3588 source package control files or upload control files.
3592 If you wish to add additional unsupported fields to
3593 these output files you should use the mechanism
3598 Fields in the main source control information file with
3599 names starting <tt>X</tt>, followed by one or more of
3600 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3601 be copied to the output files. Only the part of the
3602 field name after the hyphen will be used in the output
3603 file. Where the letter <tt>B</tt> is used the field
3604 will appear in binary package control files, where the
3605 letter <tt>S</tt> is used in source package control
3606 files and where <tt>C</tt> is used in upload control
3607 (<tt>.changes</tt>) files.
3611 For example, if the main source information control file
3614 XBS-Comment: I stand between the candle and the star.
3616 then the binary and source package control files will contain the
3619 Comment: I stand between the candle and the star.
3628 <chapt id="maintainerscripts">
3629 <heading>Package maintainer scripts and installation procedure</heading>
3632 <heading>Introduction to package maintainer scripts</heading>
3635 It is possible to supply scripts as part of a package which
3636 the package management system will run for you when your
3637 package is installed, upgraded or removed.
3641 These scripts are the control information
3642 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3643 and <prgn>postrm</prgn>. They must be proper executable files;
3644 if they are scripts (which is recommended), they must start with
3645 the usual <tt>#!</tt> convention. They should be readable and
3646 executable by anyone, and must not be world-writable.
3650 The package management system looks at the exit status from
3651 these scripts. It is important that they exit with a
3652 non-zero status if there is an error, so that the package
3653 management system can stop its processing. For shell
3654 scripts this means that you <em>almost always</em> need to
3655 use <tt>set -e</tt> (this is usually true when writing shell
3656 scripts, in fact). It is also important, of course, that
3657 they exit with a zero status if everything went well.
3661 Additionally, packages interacting with users
3662 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3663 should install a <prgn>config</prgn> script as a control
3664 information file. See <ref id="maintscriptprompt"> for details.
3668 When a package is upgraded a combination of the scripts from
3669 the old and new packages is called during the upgrade
3670 procedure. If your scripts are going to be at all
3671 complicated you need to be aware of this, and may need to
3672 check the arguments to your scripts.
3676 Broadly speaking the <prgn>preinst</prgn> is called before
3677 (a particular version of) a package is installed, and the
3678 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3679 before (a version of) a package is removed and the
3680 <prgn>postrm</prgn> afterwards.
3684 Programs called from maintainer scripts should not normally
3685 have a path prepended to them. Before installation is
3686 started, the package management system checks to see if the
3687 programs <prgn>ldconfig</prgn>,
3688 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3689 and <prgn>update-rc.d</prgn> can be found via the
3690 <tt>PATH</tt> environment variable. Those programs, and any
3691 other program that one would expect to be in the
3692 <tt>PATH</tt>, should thus be invoked without an absolute
3693 pathname. Maintainer scripts should also not reset the
3694 <tt>PATH</tt>, though they might choose to modify it by
3695 prepending or appending package-specific directories. These
3696 considerations really apply to all shell scripts.</p>
3699 <sect id="idempotency">
3700 <heading>Maintainer scripts idempotency</heading>
3703 It is necessary for the error recovery procedures that the
3704 scripts be idempotent. This means that if it is run
3705 successfully, and then it is called again, it doesn't bomb
3706 out or cause any harm, but just ensures that everything is
3707 the way it ought to be. If the first call failed, or
3708 aborted half way through for some reason, the second call
3709 should merely do the things that were left undone the first
3710 time, if any, and exit with a success status if everything
3712 This is so that if an error occurs, the user interrupts
3713 <prgn>dpkg</prgn> or some other unforeseen circumstance
3714 happens you don't leave the user with a badly-broken
3715 package when <prgn>dpkg</prgn> attempts to repeat the
3721 <sect id="controllingterminal">
3722 <heading>Controlling terminal for maintainer scripts</heading>
3725 Maintainer scripts are not guaranteed to run with a controlling
3726 terminal and may not be able to interact with the user. They
3727 must be able to fall back to noninteractive behavior if no
3728 controlling terminal is available. Maintainer scripts that
3729 prompt via a program conforming to the Debian Configuration
3730 Management Specification (see <ref id="maintscriptprompt">) may
3731 assume that program will handle falling back to noninteractive
3736 For high-priority prompts without a reasonable default answer,
3737 maintainer scripts may abort if there is no controlling
3738 terminal. However, this situation should be avoided if at all
3739 possible, since it prevents automated or unattended installs.
3740 In most cases, users will consider this to be a bug in the
3745 <sect id="exitstatus">
3746 <heading>Exit status</heading>
3749 Each script must return a zero exit status for
3750 success, or a nonzero one for failure, since the package
3751 management system looks for the exit status of these scripts
3752 and determines what action to take next based on that datum.
3756 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3761 <list compact="compact">
3763 <var>new-preinst</var> <tt>install</tt>
3766 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3769 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3772 <var>old-preinst</var> <tt>abort-upgrade</tt>
3773 <var>new-version</var>
3778 <list compact="compact">
3780 <var>postinst</var> <tt>configure</tt>
3781 <var>most-recently-configured-version</var>
3784 <var>old-postinst</var> <tt>abort-upgrade</tt>
3785 <var>new-version</var>
3788 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3789 <tt>in-favour</tt> <var>package</var>
3790 <var>new-version</var>
3793 <var>postinst</var> <tt>abort-remove</tt>
3796 <var>deconfigured's-postinst</var>
3797 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3798 <var>failed-install-package</var> <var>version</var>
3799 [<tt>removing</tt> <var>conflicting-package</var>
3805 <list compact="compact">
3807 <var>prerm</var> <tt>remove</tt>
3810 <var>old-prerm</var> <tt>upgrade</tt>
3811 <var>new-version</var>
3814 <var>new-prerm</var> <tt>failed-upgrade</tt>
3815 <var>old-version</var>
3818 <var>conflictor's-prerm</var> <tt>remove</tt>
3819 <tt>in-favour</tt> <var>package</var>
3820 <var>new-version</var>
3823 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3824 <tt>in-favour</tt> <var>package-being-installed</var>
3825 <var>version</var> [<tt>removing</tt>
3826 <var>conflicting-package</var>
3832 <list compact="compact">
3834 <var>postrm</var> <tt>remove</tt>
3837 <var>postrm</var> <tt>purge</tt>
3840 <var>old-postrm</var> <tt>upgrade</tt>
3841 <var>new-version</var>
3844 <var>new-postrm</var> <tt>failed-upgrade</tt>
3845 <var>old-version</var>
3848 <var>new-postrm</var> <tt>abort-install</tt>
3851 <var>new-postrm</var> <tt>abort-install</tt>
3852 <var>old-version</var>
3855 <var>new-postrm</var> <tt>abort-upgrade</tt>
3856 <var>old-version</var>
3859 <var>disappearer's-postrm</var> <tt>disappear</tt>
3860 <var>overwriter</var>
3861 <var>overwriter-version</var>
3867 <sect id="unpackphase">
3868 <heading>Details of unpack phase of installation or upgrade</heading>
3871 The procedure on installation/upgrade/overwrite/disappear
3872 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3873 stage of <tt>dpkg --install</tt>) is as follows. In each
3874 case, if a major error occurs (unless listed below) the
3875 actions are, in general, run backwards - this means that the
3876 maintainer scripts are run with different arguments in
3877 reverse order. These are the "error unwind" calls listed
3884 If a version of the package is already installed, call
3885 <example compact="compact">
3886 <var>old-prerm</var> upgrade <var>new-version</var>
3890 If the script runs but exits with a non-zero
3891 exit status, <prgn>dpkg</prgn> will attempt:
3892 <example compact="compact">
3893 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3895 If this works, the upgrade continues. If this
3896 does not work, the error unwind:
3897 <example compact="compact">
3898 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3900 If this works, then the old-version is
3901 "Installed", if not, the old version is in a
3902 "Half-Configured" state.
3908 If a "conflicting" package is being removed at the same time,
3909 or if any package will be broken (due to <tt>Breaks</tt>):
3912 If <tt>--auto-deconfigure</tt> is
3913 specified, call, for each package to be deconfigured
3914 due to <tt>Breaks</tt>:
3915 <example compact="compact">
3916 <var>deconfigured's-prerm</var> deconfigure \
3917 in-favour <var>package-being-installed</var> <var>version</var>
3920 <example compact="compact">
3921 <var>deconfigured's-postinst</var> abort-deconfigure \
3922 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3924 The deconfigured packages are marked as
3925 requiring configuration, so that if
3926 <tt>--install</tt> is used they will be
3927 configured again if possible.
3930 If any packages depended on a conflicting
3931 package being removed and <tt>--auto-deconfigure</tt> is
3932 specified, call, for each such package:
3933 <example compact="compact">
3934 <var>deconfigured's-prerm</var> deconfigure \
3935 in-favour <var>package-being-installed</var> <var>version</var> \
3936 removing <var>conflicting-package</var> <var>version</var>
3939 <example compact="compact">
3940 <var>deconfigured's-postinst</var> abort-deconfigure \
3941 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3942 removing <var>conflicting-package</var> <var>version</var>
3944 The deconfigured packages are marked as
3945 requiring configuration, so that if
3946 <tt>--install</tt> is used they will be
3947 configured again if possible.
3950 To prepare for removal of each conflicting package, call:
3951 <example compact="compact">
3952 <var>conflictor's-prerm</var> remove \
3953 in-favour <var>package</var> <var>new-version</var>
3956 <example compact="compact">
3957 <var>conflictor's-postinst</var> abort-remove \
3958 in-favour <var>package</var> <var>new-version</var>
3967 If the package is being upgraded, call:
3968 <example compact="compact">
3969 <var>new-preinst</var> upgrade <var>old-version</var>
3971 If this fails, we call:
3973 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3980 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3982 is called. If this works, then the old version
3983 is in an "Installed" state, or else it is left
3984 in an "Unpacked" state.
3989 If it fails, then the old version is left
3990 in an "Half-Installed" state.
3997 Otherwise, if the package had some configuration
3998 files from a previous version installed (i.e., it
3999 is in the "configuration files only" state):
4000 <example compact="compact">
4001 <var>new-preinst</var> install <var>old-version</var>
4005 <var>new-postrm</var> abort-install <var>old-version</var>
4007 If this fails, the package is left in a
4008 "Half-Installed" state, which requires a
4009 reinstall. If it works, the packages is left in
4010 a "Config-Files" state.
4013 Otherwise (i.e., the package was completely purged):
4014 <example compact="compact">
4015 <var>new-preinst</var> install
4018 <example compact="compact">
4019 <var>new-postrm</var> abort-install
4021 If the error-unwind fails, the package is in a
4022 "Half-Installed" phase, and requires a
4023 reinstall. If the error unwind works, the
4024 package is in a not installed state.
4031 The new package's files are unpacked, overwriting any
4032 that may be on the system already, for example any
4033 from the old version of the same package or from
4034 another package. Backups of the old files are kept
4035 temporarily, and if anything goes wrong the package
4036 management system will attempt to put them back as
4037 part of the error unwind.
4041 It is an error for a package to contain files which
4042 are on the system in another package, unless
4043 <tt>Replaces</tt> is used (see <ref id="replaces">).
4045 The following paragraph is not currently the case:
4046 Currently the <tt>- - force-overwrite</tt> flag is
4047 enabled, downgrading it to a warning, but this may not
4053 It is a more serious error for a package to contain a
4054 plain file or other kind of non-directory where another
4055 package has a directory (again, unless
4056 <tt>Replaces</tt> is used). This error can be
4057 overridden if desired using
4058 <tt>--force-overwrite-dir</tt>, but this is not
4063 Packages which overwrite each other's files produce
4064 behavior which, though deterministic, is hard for the
4065 system administrator to understand. It can easily
4066 lead to "missing" programs if, for example, a package
4067 is installed which overwrites a file from another
4068 package, and is then removed again.<footnote>
4069 Part of the problem is due to what is arguably a
4070 bug in <prgn>dpkg</prgn>.
4075 A directory will never be replaced by a symbolic link
4076 to a directory or vice versa; instead, the existing
4077 state (symlink or not) will be left alone and
4078 <prgn>dpkg</prgn> will follow the symlink if there is
4087 If the package is being upgraded, call
4088 <example compact="compact">
4089 <var>old-postrm</var> upgrade <var>new-version</var>
4093 If this fails, <prgn>dpkg</prgn> will attempt:
4094 <example compact="compact">
4095 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4097 If this works, installation continues. If not,
4099 <example compact="compact">
4100 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4102 If this fails, the old version is left in a
4103 "Half-Installed" state. If it works, dpkg now
4105 <example compact="compact">
4106 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4108 If this fails, the old version is left in a
4109 "Half-Installed" state. If it works, dpkg now
4111 <example compact="compact">
4112 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4114 If this fails, the old version is in an
4121 This is the point of no return - if
4122 <prgn>dpkg</prgn> gets this far, it won't back off
4123 past this point if an error occurs. This will
4124 leave the package in a fairly bad state, which
4125 will require a successful re-installation to clear
4126 up, but it's when <prgn>dpkg</prgn> starts doing
4127 things that are irreversible.
4132 Any files which were in the old version of the package
4133 but not in the new are removed.
4137 The new file list replaces the old.
4141 The new maintainer scripts replace the old.
4145 Any packages all of whose files have been overwritten
4146 during the installation, and which aren't required for
4147 dependencies, are considered to have been removed.
4148 For each such package
4151 <prgn>dpkg</prgn> calls:
4152 <example compact="compact">
4153 <var>disappearer's-postrm</var> disappear \
4154 <var>overwriter</var> <var>overwriter-version</var>
4158 The package's maintainer scripts are removed.
4161 It is noted in the status database as being in a
4162 sane state, namely not installed (any conffiles
4163 it may have are ignored, rather than being
4164 removed by <prgn>dpkg</prgn>). Note that
4165 disappearing packages do not have their prerm
4166 called, because <prgn>dpkg</prgn> doesn't know
4167 in advance that the package is going to
4174 Any files in the package we're unpacking that are also
4175 listed in the file lists of other packages are removed
4176 from those lists. (This will lobotomize the file list
4177 of the "conflicting" package if there is one.)
4181 The backup files made during installation, above, are
4187 The new package's status is now sane, and recorded as
4192 Here is another point of no return - if the
4193 conflicting package's removal fails we do not unwind
4194 the rest of the installation; the conflicting package
4195 is left in a half-removed limbo.
4200 If there was a conflicting package we go and do the
4201 removal actions (described below), starting with the
4202 removal of the conflicting package's files (any that
4203 are also in the package being installed have already
4204 been removed from the conflicting package's file list,
4205 and so do not get removed now).
4211 <sect id="configdetails"><heading>Details of configuration</heading>
4214 When we configure a package (this happens with <tt>dpkg
4215 --install</tt> and <tt>dpkg --configure</tt>), we first
4216 update any <tt>conffile</tt>s and then call:
4217 <example compact="compact">
4218 <var>postinst</var> configure <var>most-recently-configured-version</var>
4223 No attempt is made to unwind after errors during
4224 configuration. If the configuration fails, the package is in
4225 a "Failed Config" state, and an error message is generated.
4229 If there is no most recently configured version
4230 <prgn>dpkg</prgn> will pass a null argument.
4233 Historical note: Truly ancient (pre-1997) versions of
4234 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4235 (including the angle brackets) in this case. Even older
4236 ones did not pass a second argument at all, under any
4237 circumstance. Note that upgrades using such an old dpkg
4238 version are unlikely to work for other reasons, even if
4239 this old argument behavior is handled by your postinst script.
4245 <sect id="removedetails"><heading>Details of removal and/or
4246 configuration purging</heading>
4252 <example compact="compact">
4253 <var>prerm</var> remove
4257 If prerm fails during replacement due to conflict
4259 <var>conflictor's-postinst</var> abort-remove \
4260 in-favour <var>package</var> <var>new-version</var>
4264 <var>postinst</var> abort-remove
4268 If this fails, the package is in a "Half-Configured"
4269 state, or else it remains "Installed".
4273 The package's files are removed (except <tt>conffile</tt>s).
4276 <example compact="compact">
4277 <var>postrm</var> remove
4281 If it fails, there's no error unwind, and the package is in
4282 an "Half-Installed" state.
4287 All the maintainer scripts except the <prgn>postrm</prgn>
4292 If we aren't purging the package we stop here. Note
4293 that packages which have no <prgn>postrm</prgn> and no
4294 <tt>conffile</tt>s are automatically purged when
4295 removed, as there is no difference except for the
4296 <prgn>dpkg</prgn> status.
4300 The <tt>conffile</tt>s and any backup files
4301 (<tt>~</tt>-files, <tt>#*#</tt> files,
4302 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4307 <example compact="compact">
4308 <var>postrm</var> purge
4312 If this fails, the package remains in a "Config-Files"
4317 The package's file list is removed.
4326 <chapt id="relationships">
4327 <heading>Declaring relationships between packages</heading>
4329 <sect id="depsyntax">
4330 <heading>Syntax of relationship fields</heading>
4333 These fields all have a uniform syntax. They are a list of
4334 package names separated by commas.
4338 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4339 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4340 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4341 control fields of the package, which declare
4342 dependencies on other packages, the package names listed may
4343 also include lists of alternative package names, separated
4344 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4345 if any one of the alternative packages is installed, that
4346 part of the dependency is considered to be satisfied.
4350 All of the fields except for <tt>Provides</tt> may restrict
4351 their applicability to particular versions of each named
4352 package. This is done in parentheses after each individual
4353 package name; the parentheses should contain a relation from
4354 the list below followed by a version number, in the format
4355 described in <ref id="f-Version">.
4359 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4360 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4361 strictly earlier, earlier or equal, exactly equal, later or
4362 equal and strictly later, respectively. The deprecated
4363 forms <tt><</tt> and <tt>></tt> were used to mean
4364 earlier/later or equal, rather than strictly earlier/later,
4365 so they should not appear in new packages (though
4366 <prgn>dpkg</prgn> still supports them).
4370 Whitespace may appear at any point in the version
4371 specification subject to the rules in <ref
4372 id="controlsyntax">, and must appear where it's necessary to
4373 disambiguate; it is not otherwise significant. All of the
4374 relationship fields may span multiple lines. For
4375 consistency and in case of future changes to
4376 <prgn>dpkg</prgn> it is recommended that a single space be
4377 used after a version relationship and before a version
4378 number; it is also conventional to put a single space after
4379 each comma, on either side of each vertical bar, and before
4380 each open parenthesis. When wrapping a relationship field, it
4381 is conventional to do so after a comma and before the space
4382 following that comma.
4386 For example, a list of dependencies might appear as:
4387 <example compact="compact">
4390 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4395 Relationships may be restricted to a certain set of
4396 architectures. This is indicated in brackets after each
4397 individual package name and the optional version specification.
4398 The brackets enclose a list of Debian architecture names
4399 separated by whitespace. Exclamation marks may be prepended to
4400 each of the names. (It is not permitted for some names to be
4401 prepended with exclamation marks while others aren't.)
4405 For build relationship fields
4406 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4407 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4408 the current Debian host architecture is not in this list and
4409 there are no exclamation marks in the list, or it is in the list
4410 with a prepended exclamation mark, the package name and the
4411 associated version specification are ignored completely for the
4412 purposes of defining the relationships.
4417 <example compact="compact">
4419 Build-Depends-Indep: texinfo
4420 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4421 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4423 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4424 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4425 <tt>gnumach-dev</tt> only on hurd-i386.
4429 For binary relationship fields, the architecture restriction
4430 syntax is only supported in the source package control
4431 file <file>debian/control</file>. When the corresponding binary
4432 package control file is generated, the relationship will either
4433 be omitted or included without the architecture restriction
4434 based on the architecture of the binary package. This means
4435 that architecture restrictions must not be used in binary
4436 relationship fields for architecture-independent packages
4437 (<tt>Architecture: all</tt>).
4442 <example compact="compact">
4443 Depends: foo [i386], bar [amd64]
4445 becomes <tt>Depends: foo</tt> when the package is built on
4446 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4447 package is built on the <tt>amd64</tt> architecture, and omitted
4448 entirely in binary packages built on all other architectures.
4452 If the architecture-restricted dependency is part of a set of
4453 alternatives using <tt>|</tt>, that alternative is ignored
4454 completely on architectures that do not match the restriction.
4456 <example compact="compact">
4457 Build-Depends: foo [!i386] | bar [!amd64]
4459 is equivalent to <tt>bar</tt> on the i386 architecture, to
4460 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4461 bar</tt> on all other architectures.
4465 Relationships may also be restricted to a certain set of
4466 architectures using architecture wildcards. The syntax for
4467 declaring such restrictions is the same as declaring
4468 restrictions using a certain set of architectures without
4469 architecture wildcards. For example:
4470 <example compact="compact">
4471 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4473 is equivalent to <tt>foo</tt> on architectures using the Linux
4474 kernel and any cpu, <tt>bar</tt> on architectures using any
4475 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4476 using a kernel other than Linux.
4480 Note that the binary package relationship fields such as
4481 <tt>Depends</tt> appear in one of the binary package
4482 sections of the control file, whereas the build-time
4483 relationships such as <tt>Build-Depends</tt> appear in the
4484 source package section of the control file (which is the
4489 <sect id="binarydeps">
4490 <heading>Binary Dependencies - <tt>Depends</tt>,
4491 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4492 <tt>Pre-Depends</tt>
4496 Packages can declare in their control file that they have
4497 certain relationships to other packages - for example, that
4498 they may not be installed at the same time as certain other
4499 packages, and/or that they depend on the presence of others.
4503 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4504 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4505 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4506 <tt>Breaks</tt> is described in <ref id="breaks">, and
4507 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4508 rest are described below.
4512 These seven fields are used to declare a dependency
4513 relationship by one package on another. Except for
4514 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4515 depending (binary) package's control file.
4516 (<tt>Enhances</tt> appears in the recommending package's
4517 control file, and <tt>Breaks</tt> appears in the version of
4518 depended-on package which causes the named package to
4523 A <tt>Depends</tt> field takes effect <em>only</em> when a
4524 package is to be configured. It does not prevent a package
4525 being on the system in an unconfigured state while its
4526 dependencies are unsatisfied, and it is possible to replace
4527 a package whose dependencies are satisfied and which is
4528 properly installed with a different version whose
4529 dependencies are not and cannot be satisfied; when this is
4530 done the depending package will be left unconfigured (since
4531 attempts to configure it will give errors) and will not
4532 function properly. If it is necessary, a
4533 <tt>Pre-Depends</tt> field can be used, which has a partial
4534 effect even when a package is being unpacked, as explained
4535 in detail below. (The other three dependency fields,
4536 <tt>Recommends</tt>, <tt>Suggests</tt> and
4537 <tt>Enhances</tt>, are only used by the various front-ends
4538 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4539 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4543 For this reason packages in an installation run are usually
4544 all unpacked first and all configured later; this gives
4545 later versions of packages with dependencies on later
4546 versions of other packages the opportunity to have their
4547 dependencies satisfied.
4551 In case of circular dependencies, since installation or
4552 removal order honoring the dependency order can't be
4553 established, dependency loops are broken at some point
4554 (based on rules below), and some packages may not be able to
4555 rely on their dependencies being present when being
4556 installed or removed, depending on which side of the break
4557 of the circular dependency loop they happen to be on. If one
4558 of the packages in the loop has no postinst script, then the
4559 cycle will be broken at that package, so as to ensure that
4560 all postinst scripts run with the dependencies properly
4561 configured if this is possible. Otherwise the breaking point
4566 The <tt>Depends</tt> field thus allows package maintainers
4567 to impose an order in which packages should be configured.
4571 The meaning of the five dependency fields is as follows:
4573 <tag><tt>Depends</tt></tag>
4576 This declares an absolute dependency. A package will
4577 not be configured unless all of the packages listed in
4578 its <tt>Depends</tt> field have been correctly
4583 The <tt>Depends</tt> field should be used if the
4584 depended-on package is required for the depending
4585 package to provide a significant amount of
4590 The <tt>Depends</tt> field should also be used if the
4591 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4592 <prgn>postrm</prgn> scripts require the package to be
4593 present in order to run. Note, however, that the
4594 <prgn>postrm</prgn> cannot rely on any non-essential
4595 packages to be present during the <tt>purge</tt>
4599 <tag><tt>Recommends</tt></tag>
4602 This declares a strong, but not absolute, dependency.
4606 The <tt>Recommends</tt> field should list packages
4607 that would be found together with this one in all but
4608 unusual installations.
4612 <tag><tt>Suggests</tt></tag>
4614 This is used to declare that one package may be more
4615 useful with one or more others. Using this field
4616 tells the packaging system and the user that the
4617 listed packages are related to this one and can
4618 perhaps enhance its usefulness, but that installing
4619 this one without them is perfectly reasonable.
4622 <tag><tt>Enhances</tt></tag>
4624 This field is similar to Suggests but works in the
4625 opposite direction. It is used to declare that a
4626 package can enhance the functionality of another
4630 <tag><tt>Pre-Depends</tt></tag>
4633 This field is like <tt>Depends</tt>, except that it
4634 also forces <prgn>dpkg</prgn> to complete installation
4635 of the packages named before even starting the
4636 installation of the package which declares the
4637 pre-dependency, as follows:
4641 When a package declaring a pre-dependency is about to
4642 be <em>unpacked</em> the pre-dependency can be
4643 satisfied if the depended-on package is either fully
4644 configured, <em>or even if</em> the depended-on
4645 package(s) are only unpacked or in the "Half-Configured"
4646 state, provided that they have been configured
4647 correctly at some point in the past (and not removed
4648 or partially removed since). In this case, both the
4649 previously-configured and currently unpacked or
4650 "Half-Configured" versions must satisfy any version
4651 clause in the <tt>Pre-Depends</tt> field.
4655 When the package declaring a pre-dependency is about
4656 to be <em>configured</em>, the pre-dependency will be
4657 treated as a normal <tt>Depends</tt>, that is, it will
4658 be considered satisfied only if the depended-on
4659 package has been correctly configured.
4663 <tt>Pre-Depends</tt> should be used sparingly,
4664 preferably only by packages whose premature upgrade or
4665 installation would hamper the ability of the system to
4666 continue with any upgrade that might be in progress.
4670 <tt>Pre-Depends</tt> are also required if the
4671 <prgn>preinst</prgn> script depends on the named
4672 package. It is best to avoid this situation if
4680 When selecting which level of dependency to use you should
4681 consider how important the depended-on package is to the
4682 functionality of the one declaring the dependency. Some
4683 packages are composed of components of varying degrees of
4684 importance. Such a package should list using
4685 <tt>Depends</tt> the package(s) which are required by the
4686 more important components. The other components'
4687 requirements may be mentioned as Suggestions or
4688 Recommendations, as appropriate to the components' relative
4694 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4697 When one binary package declares that it breaks another,
4698 <prgn>dpkg</prgn> will refuse to allow the package which
4699 declares <tt>Breaks</tt> be installed unless the broken
4700 package is deconfigured first, and it will refuse to
4701 allow the broken package to be reconfigured.
4705 A package will not be regarded as causing breakage merely
4706 because its configuration files are still installed; it must
4707 be at least "Half-Installed".
4711 A special exception is made for packages which declare that
4712 they break their own package name or a virtual package which
4713 they provide (see below): this does not count as a real
4718 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4719 version clause; such a <tt>Breaks</tt> is introduced in the
4720 version of an (implicit or explicit) dependency which violates
4721 an assumption or reveals a bug in earlier versions of the broken
4722 package, or which takes over a file from earlier versions of the
4723 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4724 will inform higher-level package management tools that the
4725 broken package must be upgraded before the new one.
4729 If the breaking package also overwrites some files from the
4730 older package, it should use <tt>Replaces</tt> to ensure this
4731 goes smoothly. See <ref id="replaces"> for a full discussion
4732 of taking over files from other packages, including how to
4733 use <tt>Breaks</tt> in those cases.
4737 Many of the cases where <tt>Breaks</tt> should be used were
4738 previously handled with <tt>Conflicts</tt>
4739 because <tt>Breaks</tt> did not yet exist.
4740 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4741 See <ref id="conflicts"> for more information about the
4746 <sect id="conflicts">
4747 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4750 When one binary package declares a conflict with another
4751 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4752 refuse to allow them to be installed on the system at the
4753 same time. This is a stronger restriction than <tt>Breaks</tt>,
4754 which just prevents both packages from being configured at the
4755 same time. Conflicting packages cannot be unpacked on the
4756 system at the same time.
4760 If one package is to be installed, the other must be removed
4761 first. If the package being installed is marked as replacing
4762 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4763 normally be used in this case) the one on the system, or the one
4764 on the system is marked as deselected, or both packages are
4765 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4766 automatically remove the package which is causing the conflict.
4767 Otherwise, it will halt the installation of the new package with
4768 an error. This mechanism is specifically designed to produce an
4769 error when the installed package is <tt>Essential</tt>, but the
4774 A package will not cause a conflict merely because its
4775 configuration files are still installed; it must be at least
4780 A special exception is made for packages which declare a
4781 conflict with their own package name, or with a virtual
4782 package which they provide (see below): this does not
4783 prevent their installation, and allows a package to conflict
4784 with others providing a replacement for it. You use this
4785 feature when you want the package in question to be the only
4786 package providing some feature.
4790 Normally, <tt>Breaks</tt> should be used instead
4791 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4792 stronger restriction on the ordering of package installation or
4793 upgrade and can make it more difficult for the package manager
4794 to find a correct solution to an upgrade or installation
4795 problem. <tt>Breaks</tt> should be used
4797 <item>when moving a file from one package to another (see
4798 <ref id="replaces">),</item>
4799 <item>when splitting a package (a special case of the previous
4801 <item>when the breaking package exposes a bug in or interacts
4802 badly with particular versions of the broken
4805 <tt>Conflicts</tt> should be used
4807 <item>when two packages provide the same file and will
4808 continue to do so,</item>
4809 <item>in conjunction with <tt>Provides</tt> when only one
4810 package providing a given virtual facility may be installed
4811 at a time (see <ref id="virtual">),</item>
4812 <item>in other cases where one must prevent simultaneous
4813 installation of two packages for reasons that are ongoing
4814 (not fixed in a later version of one of the packages) or
4815 that must prevent both packages from being unpacked at the
4816 same time, not just configured.</item>
4818 Be aware that adding <tt>Conflicts</tt> is normally not the best
4819 solution when two packages provide the same files. Depending on
4820 the reason for that conflict, using alternatives or renaming the
4821 files is often a better approach. See, for
4822 example, <ref id="binaries">.
4826 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4827 unless two packages cannot be installed at the same time or
4828 installing them both causes one of them to be broken or
4829 unusable. Having similar functionality or performing the same
4830 tasks as another package is not sufficient reason to
4831 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4835 A <tt>Conflicts</tt> entry may have an "earlier than" version
4836 clause if the reason for the conflict is corrected in a later
4837 version of one of the packages. However, normally the presence
4838 of an "earlier than" version clause is a sign
4839 that <tt>Breaks</tt> should have been used instead. An "earlier
4840 than" version clause in <tt>Conflicts</tt>
4841 prevents <prgn>dpkg</prgn> from upgrading or installing the
4842 package which declares such a conflict until the upgrade or
4843 removal of the conflicted-with package has been completed, which
4844 is a strong restriction.
4848 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4852 As well as the names of actual ("concrete") packages, the
4853 package relationship fields <tt>Depends</tt>,
4854 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4855 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4856 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4857 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4858 may mention "virtual packages".
4862 A <em>virtual package</em> is one which appears in the
4863 <tt>Provides</tt> control field of another package. The effect
4864 is as if the package(s) which provide a particular virtual
4865 package name had been listed by name everywhere the virtual
4866 package name appears. (See also <ref id="virtual_pkg">)
4870 If there are both concrete and virtual packages of the same
4871 name, then the dependency may be satisfied (or the conflict
4872 caused) by either the concrete package with the name in
4873 question or any other concrete package which provides the
4874 virtual package with the name in question. This is so that,
4875 for example, supposing we have
4876 <example compact="compact">
4879 </example> and someone else releases an enhanced version of
4880 the <tt>bar</tt> package they can say:
4881 <example compact="compact">
4885 and the <tt>bar-plus</tt> package will now also satisfy the
4886 dependency for the <tt>foo</tt> package.
4890 If a relationship field has a version number attached, only real
4891 packages will be considered to see whether the relationship is
4892 satisfied (or the prohibition violated, for a conflict or
4893 breakage). In other words, if a version number is specified,
4894 this is a request to ignore all <tt>Provides</tt> for that
4895 package name and consider only real packages. The package
4896 manager will assume that a package providing that virtual
4897 package is not of the "right" version. A <tt>Provides</tt>
4898 field may not contain version numbers, and the version number of
4899 the concrete package which provides a particular virtual package
4900 will not be considered when considering a dependency on or
4901 conflict with the virtual package name.<footnote>
4902 It is possible that a future release of <prgn>dpkg</prgn> may
4903 add the ability to specify a version number for each virtual
4904 package it provides. This feature is not yet present,
4905 however, and is expected to be used only infrequently.
4910 To specify which of a set of real packages should be the default
4911 to satisfy a particular dependency on a virtual package, list
4912 the real package as an alternative before the virtual one.
4916 If the virtual package represents a facility that can only be
4917 provided by one real package at a time, such as
4918 the <package>mail-transport-agent</package> virtual package that
4919 requires installation of a binary that would conflict with all
4920 other providers of that virtual package (see
4921 <ref id="mail-transport-agents">), all packages providing that
4922 virtual package should also declare a conflict with it
4923 using <tt>Conflicts</tt>. This will ensure that at most one
4924 provider of that virtual package is unpacked or installed at a
4929 <sect id="replaces"><heading>Overwriting files and replacing
4930 packages - <tt>Replaces</tt></heading>
4933 Packages can declare in their control file that they should
4934 overwrite files in certain other packages, or completely replace
4935 other packages. The <tt>Replaces</tt> control field has these
4936 two distinct purposes.
4939 <sect1><heading>Overwriting files in other packages</heading>
4942 It is usually an error for a package to contain files which
4943 are on the system in another package. However, if the
4944 overwriting package declares that it <tt>Replaces</tt> the one
4945 containing the file being overwritten, then <prgn>dpkg</prgn>
4946 will replace the file from the old package with that from the
4947 new. The file will no longer be listed as "owned" by the old
4948 package and will be taken over by the new package.
4949 Normally, <tt>Breaks</tt> should be used in conjunction
4950 with <tt>Replaces</tt>.<footnote>
4951 To see why <tt>Breaks</tt> is normally needed in addition
4952 to <tt>Replaces</tt>, consider the case of a file in the
4953 package <package>foo</package> being taken over by the
4954 package <package>foo-data</package>.
4955 <tt>Replaces</tt> will allow <package>foo-data</package> to
4956 be installed and take over that file. However,
4957 without <tt>Breaks</tt>, nothing
4958 requires <package>foo</package> to be upgraded to a newer
4959 version that knows it does not include that file and instead
4960 depends on <package>foo-data</package>. Nothing would
4961 prevent the new <package>foo-data</package> package from
4962 being installed and then removed, removing the file that it
4963 took over from <package>foo</package>. After that
4964 operation, the package manager would think the system was in
4965 a consistent state, but the <package>foo</package> package
4966 would be missing one of its files.
4971 For example, if a package <package>foo</package> is split
4972 into <package>foo</package> and <package>foo-data</package>
4973 starting at version 1.2-3, <package>foo-data</package> would
4975 <example compact="compact">
4976 Replaces: foo (<< 1.2-3)
4977 Breaks: foo (<< 1.2-3)
4979 in its control file. The new version of the
4980 package <package>foo</package> would normally have the field
4981 <example compact="compact">
4982 Depends: foo-data (>= 1.2-3)
4984 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4985 the files moved into <package>foo-data</package> are not
4986 required for normal operation).
4990 If a package is completely replaced in this way, so that
4991 <prgn>dpkg</prgn> does not know of any files it still
4992 contains, it is considered to have "disappeared". It will
4993 be marked as not wanted on the system (selected for
4994 removal) and not installed. Any <tt>conffile</tt>s
4995 details noted for the package will be ignored, as they
4996 will have been taken over by the overwriting package. The
4997 package's <prgn>postrm</prgn> script will be run with a
4998 special argument to allow the package to do any final
4999 cleanup required. See <ref id="mscriptsinstact">.
5001 Replaces is a one way relationship. You have to install
5002 the replacing package after the replaced package.
5007 For this usage of <tt>Replaces</tt>, virtual packages (see
5008 <ref id="virtual">) are not considered when looking at a
5009 <tt>Replaces</tt> field. The packages declared as being
5010 replaced must be mentioned by their real names.
5014 This usage of <tt>Replaces</tt> only takes effect when both
5015 packages are at least partially on the system at once. It is
5016 not relevant if the packages conflict unless the conflict has
5021 <sect1><heading>Replacing whole packages, forcing their
5025 Second, <tt>Replaces</tt> allows the packaging system to
5026 resolve which package should be removed when there is a
5027 conflict (see <ref id="conflicts">). This usage only takes
5028 effect when the two packages <em>do</em> conflict, so that the
5029 two usages of this field do not interfere with each other.
5033 In this situation, the package declared as being replaced
5034 can be a virtual package, so for example, all mail
5035 transport agents (MTAs) would have the following fields in
5036 their control files:
5037 <example compact="compact">
5038 Provides: mail-transport-agent
5039 Conflicts: mail-transport-agent
5040 Replaces: mail-transport-agent
5042 ensuring that only one MTA can be installed at any one
5043 time. See <ref id="virtual"> for more information about this
5048 <sect id="sourcebinarydeps">
5049 <heading>Relationships between source and binary packages -
5050 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5051 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5055 Source packages that require certain binary packages to be
5056 installed or absent at the time of building the package
5057 can declare relationships to those binary packages.
5061 This is done using the <tt>Build-Depends</tt>,
5062 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5063 <tt>Build-Conflicts-Indep</tt> control fields.
5067 Build-dependencies on "build-essential" binary packages can be
5068 omitted. Please see <ref id="pkg-relations"> for more information.
5072 The dependencies and conflicts they define must be satisfied
5073 (as defined earlier for binary packages) in order to invoke
5074 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5076 There is no Build-Depends-Arch; this role is essentially
5077 met with Build-Depends. Anyone building the
5078 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5079 assumed to be building the whole package, and therefore
5080 installation of all build dependencies is required.
5083 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5084 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5085 not yet know how to check for its existence, and
5086 <tt>binary-arch</tt>. The purpose of the original split
5087 between <tt>Build-Depends</tt> and
5088 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5089 wouldn't need to install extra packages needed only for the
5090 binary-indep targets. But without a build-arch/build-indep
5091 split, this didn't work, since most of the work is done in
5092 the build target, not in the binary target.
5096 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5097 <tt>binary-arch</tt></tag>
5099 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5100 fields must be satisfied when these targets are invoked.
5102 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5103 and <tt>binary-indep</tt></tag>
5105 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5106 <tt>Build-Depends-Indep</tt>, and
5107 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5108 these targets are invoked.
5116 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5119 Packages containing shared libraries must be constructed with
5120 a little care to make sure that the shared library is always
5121 available. This is especially important for packages whose
5122 shared libraries are vitally important, such as the C library
5123 (currently <tt>libc6</tt>).
5127 Packages involving shared libraries should be split up into
5128 several binary packages. This section mostly deals with how
5129 this separation is to be accomplished; rules for files within
5130 the shared library packages are in <ref id="libraries"> instead.
5133 <sect id="sharedlibs-runtime">
5134 <heading>Run-time shared libraries</heading>
5137 The run-time shared library needs to be placed in a package
5138 whose name changes whenever the shared object version
5141 Since it is common place to install several versions of a
5142 package that just provides shared libraries, it is a
5143 good idea that the library package should not
5144 contain any extraneous non-versioned files, unless they
5145 happen to be in versioned directories.</p>
5147 The most common mechanism is to place it in a package
5149 <package><var>libraryname</var><var>soversion</var></package>,
5150 where <file><var>soversion</var></file> is the version number
5151 in the soname of the shared library<footnote>
5152 The soname is the shared object name: it's the thing
5153 that has to match exactly between building an executable
5154 and running it for the dynamic linker to be able run the
5155 program. For example, if the soname of the library is
5156 <file>libfoo.so.6</file>, the library package would be
5157 called <file>libfoo6</file>.
5159 Alternatively, if it would be confusing to directly append
5160 <var>soversion</var> to <var>libraryname</var> (e.g. because
5161 <var>libraryname</var> itself ends in a number), you may use
5162 <package><var>libraryname</var>-<var>soversion</var></package> and
5163 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5168 If you have several shared libraries built from the same
5169 source tree you may lump them all together into a single
5170 shared library package, provided that you change all of
5171 their sonames at once (so that you don't get filename
5172 clashes if you try to install different versions of the
5173 combined shared libraries package).
5177 The package should install the shared libraries under
5178 their normal names. For example, the <package>libgdbm3</package>
5179 package should install <file>libgdbm.so.3.0.0</file> as
5180 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5181 renamed or re-linked by any <prgn>prerm</prgn> or
5182 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5183 of renaming things safely without affecting running programs,
5184 and attempts to interfere with this are likely to lead to
5189 Shared libraries should not be installed executable, since
5190 the dynamic linker does not require this and trying to
5191 execute a shared library usually results in a core dump.
5195 The run-time library package should include the symbolic link that
5196 <prgn>ldconfig</prgn> would create for the shared libraries.
5197 For example, the <package>libgdbm3</package> package should include
5198 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5199 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5200 linker (for example <prgn>ld.so</prgn> or
5201 <prgn>ld-linux.so.*</prgn>) can find the library between the
5202 time that <prgn>dpkg</prgn> installs it and the time that
5203 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5205 The package management system requires the library to be
5206 placed before the symbolic link pointing to it in the
5207 <file>.deb</file> file. This is so that when
5208 <prgn>dpkg</prgn> comes to install the symlink
5209 (overwriting the previous symlink pointing at an older
5210 version of the library), the new shared library is already
5211 in place. In the past, this was achieved by creating the
5212 library in the temporary packaging directory before
5213 creating the symlink. Unfortunately, this was not always
5214 effective, since the building of the tar file in the
5215 <file>.deb</file> depended on the behavior of the underlying
5216 file system. Some file systems (such as reiserfs) reorder
5217 the files so that the order of creation is forgotten.
5218 Since version 1.7.0, <prgn>dpkg</prgn>
5219 reorders the files itself as necessary when building a
5220 package. Thus it is no longer important to concern
5221 oneself with the order of file creation.
5225 <sect1 id="ldconfig">
5226 <heading><tt>ldconfig</tt></heading>
5229 Any package installing shared libraries in one of the default
5230 library directories of the dynamic linker (which are currently
5231 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5232 listed in <file>/etc/ld.so.conf</file><footnote>
5234 <list compact="compact">
5235 <item>/usr/local/lib</item>
5236 <item>/usr/lib/libc5-compat</item>
5237 <item>/lib/libc5-compat</item>
5240 must use <prgn>ldconfig</prgn> to update the shared library
5245 The package maintainer scripts must only call
5246 <prgn>ldconfig</prgn> under these circumstances:
5247 <list compact="compact">
5248 <item>When the <prgn>postinst</prgn> script is run with a
5249 first argument of <tt>configure</tt>, the script must call
5250 <prgn>ldconfig</prgn>, and may optionally invoke
5251 <prgn>ldconfig</prgn> at other times.
5253 <item>When the <prgn>postrm</prgn> script is run with a
5254 first argument of <tt>remove</tt>, the script should call
5255 <prgn>ldconfig</prgn>.
5260 During install or upgrade, the preinst is called before
5261 the new files are installed, so calling "ldconfig" is
5262 pointless. The preinst of an existing package can also be
5263 called if an upgrade fails. However, this happens during
5264 the critical time when a shared libs may exist on-disk
5265 under a temporary name. Thus, it is dangerous and
5266 forbidden by current policy to call "ldconfig" at this
5271 When a package is installed or upgraded, "postinst
5272 configure" runs after the new files are safely on-disk.
5273 Since it is perfectly safe to invoke ldconfig
5274 unconditionally in a postinst, it is OK for a package to
5275 simply put ldconfig in its postinst without checking the
5276 argument. The postinst can also be called to recover from
5277 a failed upgrade. This happens before any new files are
5278 unpacked, so there is no reason to call "ldconfig" at this
5283 For a package that is being removed, prerm is
5284 called with all the files intact, so calling ldconfig is
5285 useless. The other calls to "prerm" happen in the case of
5286 upgrade at a time when all the files of the old package
5287 are on-disk, so again calling "ldconfig" is pointless.
5291 postrm, on the other hand, is called with the "remove"
5292 argument just after the files are removed, so this is
5293 the proper time to call "ldconfig" to notify the system
5294 of the fact that the shared libraries from the package
5295 are removed. The postrm can be called at several other
5296 times. At the time of "postrm purge", "postrm
5297 abort-install", or "postrm abort-upgrade", calling
5298 "ldconfig" is useless because the shared lib files are
5299 not on-disk. However, when "postrm" is invoked with
5300 arguments "upgrade", "failed-upgrade", or "disappear", a
5301 shared lib may exist on-disk under a temporary filename.
5309 <sect id="sharedlibs-support-files">
5310 <heading>Shared library support files</heading>
5313 If your package contains files whose names do not change with
5314 each change in the library shared object version, you must not
5315 put them in the shared library package. Otherwise, several
5316 versions of the shared library cannot be installed at the same
5317 time without filename clashes, making upgrades and transitions
5318 unnecessarily difficult.
5322 It is recommended that supporting files and run-time support
5323 programs that do not need to be invoked manually by users, but
5324 are nevertheless required for the package to function, be placed
5325 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5326 preferably under <file>/usr/lib/</file><var>package-name</var>.
5327 If the program or file is architecture independent, the
5328 recommendation is for it to be placed in a subdirectory of
5329 <file>/usr/share</file> instead, preferably under
5330 <file>/usr/share/</file><var>package-name</var>. Following the
5331 <var>package-name</var> naming convention ensures that the file
5332 names change when the shared object version changes.
5336 Run-time support programs that use the shared library but are
5337 not required for the library to function or files used by the
5338 shared library that can be used by any version of the shared
5339 library package should instead be put in a separate package.
5340 This package might typically be named
5341 <package><var>libraryname</var>-tools</package>; note the
5342 absence of the <var>soversion</var> in the package name.
5346 Files and support programs only useful when compiling software
5347 against the library should be included in the development
5348 package for the library.<footnote>
5349 For example, a <file><var>package-name</var>-config</file>
5350 script or <package>pkg-config</package> configuration files.
5355 <sect id="sharedlibs-static">
5356 <heading>Static libraries</heading>
5359 The static library (<file><var>libraryname.a</var></file>)
5360 is usually provided in addition to the shared version.
5361 It is placed into the development package (see below).
5365 In some cases, it is acceptable for a library to be
5366 available in static form only; these cases include:
5368 <item>libraries for languages whose shared library support
5369 is immature or unstable</item>
5370 <item>libraries whose interfaces are in flux or under
5371 development (commonly the case when the library's
5372 major version number is zero, or where the ABI breaks
5373 across patchlevels)</item>
5374 <item>libraries which are explicitly intended to be
5375 available only in static form by their upstream
5380 <sect id="sharedlibs-dev">
5381 <heading>Development files</heading>
5384 If there are development files associated with a shared library,
5385 the source package needs to generate a binary development package
5386 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5387 or if you prefer only to support one development version at a
5388 time, <package><var>libraryname</var>-dev</package>. Installing
5389 the development package must result in installation of all the
5390 development files necessary for compiling programs against that
5391 shared library.<footnote>
5392 This wording allows the development files to be split into
5393 several packages, such as a separate architecture-independent
5394 <package><var>libraryname</var>-headers</package>, provided that
5395 the development package depends on all the required additional
5401 In case several development versions of a library exist, you may
5402 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5403 <ref id="conflicts">) to ensure that the user only installs one
5404 development version at a time (as different development versions are
5405 likely to have the same header files in them, which would cause a
5406 filename clash if both were installed).
5410 The development package should contain a symlink for the associated
5411 shared library without a version number. For example, the
5412 <package>libgdbm-dev</package> package should include a symlink
5413 from <file>/usr/lib/libgdbm.so</file> to
5414 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5415 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5416 <file>libgdbm.so</file> when compiling dynamically.
5420 <sect id="sharedlibs-intradeps">
5421 <heading>Dependencies between the packages of the same library</heading>
5424 Typically the development version should have an exact
5425 version dependency on the runtime library, to make sure that
5426 compilation and linking happens correctly. The
5427 <tt>${binary:Version}</tt> substitution variable can be
5428 useful for this purpose.
5430 Previously, <tt>${Source-Version}</tt> was used, but its name
5431 was confusing and it has been deprecated since dpkg 1.13.19.
5436 <sect id="sharedlibs-shlibdeps">
5437 <heading>Dependencies between the library and other packages -
5438 the <tt>shlibs</tt> system</heading>
5441 If a package contains a binary or library which links to a
5442 shared library, we must ensure that when the package is
5443 installed on the system, all of the libraries needed are
5444 also installed. This requirement led to the creation of the
5445 <tt>shlibs</tt> system, which is very simple in its design:
5446 any package which <em>provides</em> a shared library also
5447 provides information on the package dependencies required to
5448 ensure the presence of this library, and any package which
5449 <em>uses</em> a shared library uses this information to
5450 determine the dependencies it requires. The files which
5451 contain the mapping from shared libraries to the necessary
5452 dependency information are called <file>shlibs</file> files.
5456 When a package is built which contains any shared libraries, it
5457 must provide a <file>shlibs</file> file for other packages to
5458 use. When a package is built which contains any shared
5459 libraries or compiled binaries, it must run
5460 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5461 on these to determine the libraries used and hence the
5462 dependencies needed by this package.<footnote>
5464 <prgn>dpkg-shlibdeps</prgn> will use a program
5465 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5466 the libraries directly needed by the binaries or shared
5467 libraries in the package.
5471 We say that a binary <tt>foo</tt> <em>directly</em> uses
5472 a library <tt>libbar</tt> if it is explicitly linked
5473 with that library (that is, the library is listed in the ELF
5474 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5475 to the link line when the binary is created). Other
5476 libraries that are needed by <tt>libbar</tt> are linked
5477 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5478 linker will load them automatically when it loads
5479 <tt>libbar</tt>. A package should depend on the libraries
5480 it directly uses, but not the libraries it indirectly uses.
5481 The dependencies for those libraries will automatically pull
5482 in the other libraries.
5486 A good example of where this helps is the following. We
5487 could update <tt>libimlib</tt> with a new version that
5488 supports a new graphics format called dgf (but retaining the
5489 same major version number) and depends on <tt>libdgf</tt>.
5490 If we used <prgn>ldd</prgn> to add dependencies for every
5491 library directly or indirectly linked with a binary, every
5492 package that uses <tt>libimlib</tt> would need to be
5493 recompiled so it would also depend on <tt>libdgf</tt> or it
5494 wouldn't run due to missing symbols. Since dependencies are
5495 only added based on ELF <tt>NEEDED</tt> attribute, packages
5496 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5497 having the dependency on <tt>libdgf</tt> and so they would
5498 not need rebuilding.
5504 In the following sections, we will first describe where the
5505 various <tt>shlibs</tt> files are to be found, then how to
5506 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5507 file format and how to create them if your package contains a
5512 <heading>The <tt>shlibs</tt> files present on the system</heading>
5515 There are several places where <tt>shlibs</tt> files are
5516 found. The following list gives them in the order in which
5518 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5519 (The first one which gives the required information is used.)
5525 <p><file>debian/shlibs.local</file></p>
5528 This lists overrides for this package. This file should
5529 normally not be used, but may be needed temporarily in
5530 unusual situations to work around bugs in other packages,
5531 or in unusual cases where the normally declared dependency
5532 information in the installed <file>shlibs</file> file for
5533 a library cannot be used. This file overrides information
5534 obtained from any other source.
5539 <p><file>/etc/dpkg/shlibs.override</file></p>
5542 This lists global overrides. This list is normally
5543 empty. It is maintained by the local system
5549 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5552 When packages are being built,
5553 any <file>debian/shlibs</file> files are copied into the
5554 control information file area of the temporary build
5555 directory and given the name <file>shlibs</file>. These
5556 files give details of any shared libraries included in the
5557 same package.<footnote>
5558 An example may help here. Let us say that the source
5559 package <tt>foo</tt> generates two binary
5560 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5561 When building the binary packages, the two packages are
5562 created in the directories <file>debian/libfoo2</file>
5563 and <file>debian/foo-runtime</file> respectively.
5564 (<file>debian/tmp</file> could be used instead of one of
5565 these.) Since <tt>libfoo2</tt> provides the
5566 <tt>libfoo</tt> shared library, it will require a
5567 <tt>shlibs</tt> file, which will be installed in
5568 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5569 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5570 When <prgn>dpkg-shlibdeps</prgn> is run on the
5571 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5573 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5574 determine whether <tt>foo-prog</tt>'s library
5575 dependencies are satisfied by any of the libraries
5576 provided by <tt>libfoo2</tt>. For this reason,
5577 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5578 the individual binary packages' <tt>shlibs</tt> files
5579 have been installed into the build directory.
5585 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5588 These are the <file>shlibs</file> files corresponding to
5589 all of the packages installed on the system, and are
5590 maintained by the relevant package maintainers.
5595 <p><file>/etc/dpkg/shlibs.default</file></p>
5598 This file lists any shared libraries whose packages
5599 have failed to provide correct <file>shlibs</file> files.
5600 It was used when the <file>shlibs</file> setup was first
5601 introduced, but it is now normally empty. It is
5602 maintained by the <tt>dpkg</tt> maintainer.
5610 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5611 <file>shlibs</file> files</heading>
5615 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5616 into your <file>debian/rules</file> file. If your package
5617 contains only compiled binaries and libraries (but no scripts),
5618 you can use a command such as:
5619 <example compact="compact">
5620 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5621 debian/tmp/usr/lib/*
5623 Otherwise, you will need to explicitly list the compiled
5624 binaries and libraries.<footnote>
5625 If you are using <tt>debhelper</tt>, the
5626 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5627 It will also correctly handle multi-binary packages.
5632 This command puts the dependency information into the
5633 <file>debian/substvars</file> file, which is then used by
5634 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5635 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5636 field in the control file for this to work.
5640 If you have multiple binary packages, you will need to call
5641 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5642 compiled libraries or binaries. In such a case, you will
5643 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5644 utilities to specify a different <file>substvars</file> file.
5648 If you are creating a udeb for use in the Debian Installer,
5649 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5650 should use the dependency line of type <tt>udeb</tt> by
5651 adding the <tt>-tudeb</tt> option<footnote>
5652 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5653 will automatically add this option if it knows it is
5655 </footnote>. If there is no dependency line of
5656 type <tt>udeb</tt> in the <file>shlibs</file>
5657 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5662 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5663 <ref id="pkg-dpkg-shlibdeps"> and
5664 <manref name="dpkg-shlibdeps" section="1">.
5669 <heading>The <file>shlibs</file> File Format</heading>
5672 Each <file>shlibs</file> file has the same format. Lines
5673 beginning with <tt>#</tt> are considered to be comments and
5674 are ignored. Each line is of the form:
5675 <example compact="compact">
5676 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5681 We will explain this by reference to the example of the
5682 <tt>zlib1g</tt> package, which (at the time of writing)
5683 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5687 <var>type</var> is an optional element that indicates the type
5688 of package for which the line is valid. The only type currently
5689 in use is <tt>udeb</tt>. The colon and space after the type are
5694 <var>library-name</var> is the name of the shared library,
5695 in this case <tt>libz</tt>. (This must match the name part
5696 of the soname, see below.)
5700 <var>soname-version</var> is the version part of the soname of
5701 the library. The soname is the thing that must exactly match
5702 for the library to be recognized by the dynamic linker, and is
5704 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5705 example, <tt>libz.so.1</tt>.<footnote>
5706 This can be determined using the command
5707 <example compact="compact">
5708 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5711 The version part is the part which comes after
5712 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5713 instead be of the form
5714 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5715 as <tt>libdb-4.8.so</tt>, in which case the name would
5716 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5720 <var>dependencies</var> has the same syntax as a dependency
5721 field in a binary package control file. It should give
5722 details of which packages are required to satisfy a binary
5723 built against the version of the library contained in the
5724 package. See <ref id="depsyntax"> for details.
5728 In our example, if the first version of the <tt>zlib1g</tt>
5729 package which contained a minor number of at least
5730 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5731 <tt>shlibs</tt> entry for this library could say:
5732 <example compact="compact">
5733 libz 1 zlib1g (>= 1:1.1.3)
5735 The version-specific dependency is to avoid warnings from
5736 the dynamic linker about using older shared libraries with
5741 As zlib1g also provides a udeb containing the shared library,
5742 there would also be a second line:
5743 <example compact="compact">
5744 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5750 <heading>Providing a <file>shlibs</file> file</heading>
5753 If your package provides a shared library, you need to create
5754 a <file>shlibs</file> file following the format described above.
5755 It is usual to call this file <file>debian/shlibs</file> (but if
5756 you have multiple binary packages, you might want to call it
5757 <file>debian/shlibs.<var>package</var></file> instead). Then
5758 let <file>debian/rules</file> install it in the control
5759 information file area:
5760 <example compact="compact">
5761 install -m644 debian/shlibs debian/tmp/DEBIAN
5763 or, in the case of a multi-binary package:
5764 <example compact="compact">
5765 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5767 An alternative way of doing this is to create the
5768 <file>shlibs</file> file in the control information file area
5769 directly from <file>debian/rules</file> without using
5770 a <file>debian/shlibs</file> file at all,<footnote>
5771 This is what <prgn>dh_makeshlibs</prgn> in
5772 the <package>debhelper</package> suite does. If your package
5773 also has a udeb that provides a shared
5774 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5775 the <tt>udeb:</tt> lines if you specify the name of the udeb
5776 with the <tt>--add-udeb</tt> option.
5778 since the <file>debian/shlibs</file> file itself is ignored by
5779 <prgn>dpkg-shlibdeps</prgn>.
5783 As <prgn>dpkg-shlibdeps</prgn> reads the
5784 <file>DEBIAN/shlibs</file> files in all of the binary packages
5785 being built from this source package, all of the
5786 <file>DEBIAN/shlibs</file> files should be installed before
5787 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5795 <chapt id="opersys"><heading>The Operating System</heading>
5798 <heading>File system hierarchy</heading>
5802 <heading>File System Structure</heading>
5805 The location of all installed files and directories must
5806 comply with the Filesystem Hierarchy Standard (FHS),
5807 version 2.3, with the exceptions noted below, and except
5808 where doing so would violate other terms of Debian
5809 Policy. The following exceptions to the FHS apply:
5814 The optional rules related to user specific
5815 configuration files for applications are stored in
5816 the user's home directory are relaxed. It is
5817 recommended that such files start with the
5818 '<tt>.</tt>' character (a "dot file"), and if an
5819 application needs to create more than one dot file
5820 then the preferred placement is in a subdirectory
5821 with a name starting with a '.' character, (a "dot
5822 directory"). In this case it is recommended the
5823 configuration files not start with the '.'
5829 The requirement for amd64 to use <file>/lib64</file>
5830 for 64 bit binaries is removed.
5835 The requirement for object files, internal binaries, and
5836 libraries, including <file>libc.so.*</file>, to be located
5837 directly under <file>/lib{,32}</file> and
5838 <file>/usr/lib{,32}</file> is amended, permitting files
5839 to instead be installed to
5840 <file>/lib/<var>triplet</var></file> and
5841 <file>/usr/lib/<var>triplet</var></file>, where
5842 <tt><var>triplet</var></tt> is the value returned by
5843 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5844 architecture of the package. Packages may <em>not</em>
5845 install files to any <var>triplet</var> path other
5846 than the one matching the architecture of that package;
5847 for instance, an <tt>Architecture: amd64</tt> package
5848 containing 32-bit x86 libraries may not install these
5849 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5851 This is necessary in order to reserve the directories for
5852 use in cross-installation of library packages from other
5853 architectures, as part of the planned deployment of
5858 Applications may also use a single subdirectory under
5859 <file>/usr/lib/<var>triplet</var></file>.
5862 The execution time linker/loader, ld*, must still be made
5863 available in the existing location under /lib or /lib64
5864 since this is part of the ELF ABI for the architecture.
5869 The requirement that
5870 <file>/usr/local/share/man</file> be "synonymous"
5871 with <file>/usr/local/man</file> is relaxed to a
5876 The requirement that windowmanagers with a single
5877 configuration file call it <file>system.*wmrc</file>
5878 is removed, as is the restriction that the window
5879 manager subdirectory be named identically to the
5880 window manager name itself.
5885 The requirement that boot manager configuration
5886 files live in <file>/etc</file>, or at least are
5887 symlinked there, is relaxed to a recommendation.
5892 The following directories in the root filesystem are
5893 additionally allowed: <file>/sys</file> and
5894 <file>/selinux</file>. <footnote>These directories
5895 are used as mount points to mount virtual filesystems
5896 to get access to kernel information.</footnote>
5903 The version of this document referred here can be
5904 found in the <tt>debian-policy</tt> package or on <url
5905 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5906 name="FHS (Debian copy)"> alongside this manual (or, if
5907 you have the <package>debian-policy</package> installed,
5909 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5910 (local copy)">). The
5911 latest version, which may be a more recent version, may
5913 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5914 Specific questions about following the standard may be
5915 asked on the <tt>debian-devel</tt> mailing list, or
5916 referred to the FHS mailing list (see the
5917 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5923 <heading>Site-specific programs</heading>
5926 As mandated by the FHS, packages must not place any
5927 files in <file>/usr/local</file>, either by putting them in
5928 the file system archive to be unpacked by <prgn>dpkg</prgn>
5929 or by manipulating them in their maintainer scripts.
5933 However, the package may create empty directories below
5934 <file>/usr/local</file> so that the system administrator knows
5935 where to place site-specific files. These are not
5936 directories <em>in</em> <file>/usr/local</file>, but are
5937 children of directories in <file>/usr/local</file>. These
5938 directories (<file>/usr/local/*/dir/</file>)
5939 should be removed on package removal if they are
5944 Note that this applies only to
5945 directories <em>below</em> <file>/usr/local</file>,
5946 not <em>in</em> <file>/usr/local</file>. Packages must
5947 not create sub-directories in the
5948 directory <file>/usr/local</file> itself, except those
5949 listed in FHS, section 4.5. However, you may create
5950 directories below them as you wish. You must not remove
5951 any of the directories listed in 4.5, even if you created
5956 Since <file>/usr/local</file> can be mounted read-only from a
5957 remote server, these directories must be created and
5958 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5959 maintainer scripts and not be included in the
5960 <file>.deb</file> archive. These scripts must not fail if
5961 either of these operations fail.
5965 For example, the <tt>emacsen-common</tt> package could
5966 contain something like
5967 <example compact="compact">
5968 if [ ! -e /usr/local/share/emacs ]
5970 if mkdir /usr/local/share/emacs 2>/dev/null
5972 chown root:staff /usr/local/share/emacs
5973 chmod 2775 /usr/local/share/emacs
5977 in its <prgn>postinst</prgn> script, and
5978 <example compact="compact">
5979 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5980 rmdir /usr/local/share/emacs 2>/dev/null || true
5982 in the <prgn>prerm</prgn> script. (Note that this form is
5983 used to ensure that if the script is interrupted, the
5984 directory <file>/usr/local/share/emacs</file> will still be
5989 If you do create a directory in <file>/usr/local</file> for
5990 local additions to a package, you should ensure that
5991 settings in <file>/usr/local</file> take precedence over the
5992 equivalents in <file>/usr</file>.
5996 However, because <file>/usr/local</file> and its contents are
5997 for exclusive use of the local administrator, a package
5998 must not rely on the presence or absence of files or
5999 directories in <file>/usr/local</file> for normal operation.
6003 The <file>/usr/local</file> directory itself and all the
6004 subdirectories created by the package should (by default) have
6005 permissions 2775 (group-writable and set-group-id) and be
6006 owned by <tt>root:staff</tt>.
6011 <heading>The system-wide mail directory</heading>
6013 The system-wide mail directory
6014 is <file>/var/mail</file>. This directory is part of the
6015 base system and should not be owned by any particular mail
6016 agents. The use of the old
6017 location <file>/var/spool/mail</file> is deprecated, even
6018 though the spool may still be physically located there.
6024 <heading>Users and groups</heading>
6027 <heading>Introduction</heading>
6029 The Debian system can be configured to use either plain or
6034 Some user ids (UIDs) and group ids (GIDs) are reserved
6035 globally for use by certain packages. Because some
6036 packages need to include files which are owned by these
6037 users or groups, or need the ids compiled into binaries,
6038 these ids must be used on any Debian system only for the
6039 purpose for which they are allocated. This is a serious
6040 restriction, and we should avoid getting in the way of
6041 local administration policies. In particular, many sites
6042 allocate users and/or local system groups starting at 100.
6046 Apart from this we should have dynamically allocated ids,
6047 which should by default be arranged in some sensible
6048 order, but the behavior should be configurable.
6052 Packages other than <tt>base-passwd</tt> must not modify
6053 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6054 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6059 <heading>UID and GID classes</heading>
6061 The UID and GID numbers are divided into classes as
6067 Globally allocated by the Debian project, the same
6068 on every Debian system. These ids will appear in
6069 the <file>passwd</file> and <file>group</file> files of all
6070 Debian systems, new ids in this range being added
6071 automatically as the <tt>base-passwd</tt> package is
6076 Packages which need a single statically allocated
6077 uid or gid should use one of these; their
6078 maintainers should ask the <tt>base-passwd</tt>
6086 Dynamically allocated system users and groups.
6087 Packages which need a user or group, but can have
6088 this user or group allocated dynamically and
6089 differently on each system, should use <tt>adduser
6090 --system</tt> to create the group and/or user.
6091 <prgn>adduser</prgn> will check for the existence of
6092 the user or group, and if necessary choose an unused
6093 id based on the ranges specified in
6094 <file>adduser.conf</file>.
6098 <tag>1000-59999:</tag>
6101 Dynamically allocated user accounts. By default
6102 <prgn>adduser</prgn> will choose UIDs and GIDs for
6103 user accounts in this range, though
6104 <file>adduser.conf</file> may be used to modify this
6109 <tag>60000-64999:</tag>
6112 Globally allocated by the Debian project, but only
6113 created on demand. The ids are allocated centrally
6114 and statically, but the actual accounts are only
6115 created on users' systems on demand.
6119 These ids are for packages which are obscure or
6120 which require many statically-allocated ids. These
6121 packages should check for and create the accounts in
6122 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6123 <prgn>adduser</prgn> if it has this facility) if
6124 necessary. Packages which are likely to require
6125 further allocations should have a "hole" left after
6126 them in the allocation, to give them room to
6131 <tag>65000-65533:</tag>
6139 User <tt>nobody</tt>. The corresponding gid refers
6140 to the group <tt>nogroup</tt>.
6147 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6148 not</em> be used, because it is the error return
6157 <sect id="sysvinit">
6158 <heading>System run levels and <file>init.d</file> scripts</heading>
6160 <sect1 id="/etc/init.d">
6161 <heading>Introduction</heading>
6164 The <file>/etc/init.d</file> directory contains the scripts
6165 executed by <prgn>init</prgn> at boot time and when the
6166 init state (or "runlevel") is changed (see <manref
6167 name="init" section="8">).
6171 There are at least two different, yet functionally
6172 equivalent, ways of handling these scripts. For the sake
6173 of simplicity, this document describes only the symbolic
6174 link method. However, it must not be assumed by maintainer
6175 scripts that this method is being used, and any automated
6176 manipulation of the various runlevel behaviors by
6177 maintainer scripts must be performed using
6178 <prgn>update-rc.d</prgn> as described below and not by
6179 manually installing or removing symlinks. For information
6180 on the implementation details of the other method,
6181 implemented in the <tt>file-rc</tt> package, please refer
6182 to the documentation of that package.
6186 These scripts are referenced by symbolic links in the
6187 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6188 runlevels, <prgn>init</prgn> looks in the directory
6189 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6190 execute, where <tt><var>n</var></tt> is the runlevel that
6191 is being changed to, or <tt>S</tt> for the boot-up
6196 The names of the links all have the form
6197 <file>S<var>mm</var><var>script</var></file> or
6198 <file>K<var>mm</var><var>script</var></file> where
6199 <var>mm</var> is a two-digit number and <var>script</var>
6200 is the name of the script (this should be the same as the
6201 name of the actual script in <file>/etc/init.d</file>).
6205 When <prgn>init</prgn> changes runlevel first the targets
6206 of the links whose names start with a <tt>K</tt> are
6207 executed, each with the single argument <tt>stop</tt>,
6208 followed by the scripts prefixed with an <tt>S</tt>, each
6209 with the single argument <tt>start</tt>. (The links are
6210 those in the <file>/etc/rc<var>n</var>.d</file> directory
6211 corresponding to the new runlevel.) The <tt>K</tt> links
6212 are responsible for killing services and the <tt>S</tt>
6213 link for starting services upon entering the runlevel.
6217 For example, if we are changing from runlevel 2 to
6218 runlevel 3, init will first execute all of the <tt>K</tt>
6219 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6220 all of the <tt>S</tt> prefixed scripts in that directory.
6221 The links starting with <tt>K</tt> will cause the
6222 referred-to file to be executed with an argument of
6223 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6228 The two-digit number <var>mm</var> is used to determine
6229 the order in which to run the scripts: low-numbered links
6230 have their scripts run first. For example, the
6231 <tt>K20</tt> scripts will be executed before the
6232 <tt>K30</tt> scripts. This is used when a certain service
6233 must be started before another. For example, the name
6234 server <prgn>bind</prgn> might need to be started before
6235 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6236 can set up its access lists. In this case, the script
6237 that starts <prgn>bind</prgn> would have a lower number
6238 than the script that starts <prgn>inn</prgn> so that it
6240 <example compact="compact">
6247 The two runlevels 0 (halt) and 6 (reboot) are slightly
6248 different. In these runlevels, the links with an
6249 <tt>S</tt> prefix are still called after those with a
6250 <tt>K</tt> prefix, but they too are called with the single
6251 argument <tt>stop</tt>.
6255 <sect1 id="writing-init">
6256 <heading>Writing the scripts</heading>
6259 Packages that include daemons for system services should
6260 place scripts in <file>/etc/init.d</file> to start or stop
6261 services at boot time or during a change of runlevel.
6262 These scripts should be named
6263 <file>/etc/init.d/<var>package</var></file>, and they should
6264 accept one argument, saying what to do:
6267 <tag><tt>start</tt></tag>
6268 <item>start the service,</item>
6270 <tag><tt>stop</tt></tag>
6271 <item>stop the service,</item>
6273 <tag><tt>restart</tt></tag>
6274 <item>stop and restart the service if it's already running,
6275 otherwise start the service</item>
6277 <tag><tt>reload</tt></tag>
6278 <item><p>cause the configuration of the service to be
6279 reloaded without actually stopping and restarting
6282 <tag><tt>force-reload</tt></tag>
6283 <item>cause the configuration to be reloaded if the
6284 service supports this, otherwise restart the
6288 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6289 <tt>force-reload</tt> options should be supported by all
6290 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6295 The <file>init.d</file> scripts must ensure that they will
6296 behave sensibly (i.e., returning success and not starting
6297 multiple copies of a service) if invoked with <tt>start</tt>
6298 when the service is already running, or with <tt>stop</tt>
6299 when it isn't, and that they don't kill unfortunately-named
6300 user processes. The best way to achieve this is usually to
6301 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6306 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6307 scripts. Writing correct <file>init.d</file> scripts requires
6308 accepting various error exit statuses when daemons are already
6309 running or already stopped without aborting
6310 the <file>init.d</file> script, and common <file>init.d</file>
6311 function libraries are not safe to call with <tt>set -e</tt>
6313 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6314 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6315 in effect and echoing status messages to the console fails,
6317 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6318 to not use <tt>set -e</tt> and instead check the result of
6319 each command separately.
6323 If a service reloads its configuration automatically (as
6324 in the case of <prgn>cron</prgn>, for example), the
6325 <tt>reload</tt> option of the <file>init.d</file> script
6326 should behave as if the configuration has been reloaded
6331 The <file>/etc/init.d</file> scripts must be treated as
6332 configuration files, either (if they are present in the
6333 package, that is, in the .deb file) by marking them as
6334 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6335 by managing them correctly in the maintainer scripts (see
6336 <ref id="config-files">). This is important since we want
6337 to give the local system administrator the chance to adapt
6338 the scripts to the local system, e.g., to disable a
6339 service without de-installing the package, or to specify
6340 some special command line options when starting a service,
6341 while making sure their changes aren't lost during the next
6346 These scripts should not fail obscurely when the
6347 configuration files remain but the package has been
6348 removed, as configuration files remain on the system after
6349 the package has been removed. Only when <prgn>dpkg</prgn>
6350 is executed with the <tt>--purge</tt> option will
6351 configuration files be removed. In particular, as the
6352 <file>/etc/init.d/<var>package</var></file> script itself is
6353 usually a <tt>conffile</tt>, it will remain on the system
6354 if the package is removed but not purged. Therefore, you
6355 should include a <tt>test</tt> statement at the top of the
6357 <example compact="compact">
6358 test -f <var>program-executed-later-in-script</var> || exit 0
6363 Often there are some variables in the <file>init.d</file>
6364 scripts whose values control the behavior of the scripts,
6365 and which a system administrator is likely to want to
6366 change. As the scripts themselves are frequently
6367 <tt>conffile</tt>s, modifying them requires that the
6368 administrator merge in their changes each time the package
6369 is upgraded and the <tt>conffile</tt> changes. To ease
6370 the burden on the system administrator, such configurable
6371 values should not be placed directly in the script.
6372 Instead, they should be placed in a file in
6373 <file>/etc/default</file>, which typically will have the same
6374 base name as the <file>init.d</file> script. This extra file
6375 should be sourced by the script when the script runs. It
6376 must contain only variable settings and comments in SUSv3
6377 <prgn>sh</prgn> format. It may either be a
6378 <tt>conffile</tt> or a configuration file maintained by
6379 the package maintainer scripts. See <ref id="config-files">
6384 To ensure that vital configurable values are always
6385 available, the <file>init.d</file> script should set default
6386 values for each of the shell variables it uses, either
6387 before sourcing the <file>/etc/default/</file> file or
6388 afterwards using something like the <tt>:
6389 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6390 script must behave sensibly and not fail if the
6391 <file>/etc/default</file> file is deleted.
6395 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6396 as temporary filesystems<footnote>
6397 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6398 options in <file>/etc/default/rcS</file>.
6399 </footnote>, so the <file>init.d</file> scripts must handle this
6400 correctly. This will typically amount to creating any required
6401 subdirectories dynamically when the <file>init.d</file> script
6402 is run, rather than including them in the package and relying on
6403 <prgn>dpkg</prgn> to create them.
6408 <heading>Interfacing with the initscript system</heading>
6411 Maintainers should use the abstraction layer provided by
6412 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6413 programs to deal with initscripts in their packages'
6414 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6415 and <prgn>postrm</prgn>.
6419 Directly managing the /etc/rc?.d links and directly
6420 invoking the <file>/etc/init.d/</file> initscripts should
6421 be done only by packages providing the initscript
6422 subsystem (such as <prgn>sysv-rc</prgn> and
6423 <prgn>file-rc</prgn>).
6427 <heading>Managing the links</heading>
6430 The program <prgn>update-rc.d</prgn> is provided for
6431 package maintainers to arrange for the proper creation and
6432 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6433 or their functional equivalent if another method is being
6434 used. This may be used by maintainers in their packages'
6435 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6439 You must not include any <file>/etc/rc<var>n</var>.d</file>
6440 symbolic links in the actual archive or manually create or
6441 remove the symbolic links in maintainer scripts; you must
6442 use the <prgn>update-rc.d</prgn> program instead. (The
6443 former will fail if an alternative method of maintaining
6444 runlevel information is being used.) You must not include
6445 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6446 in the archive either. (Only the <tt>sysvinit</tt>
6451 By default <prgn>update-rc.d</prgn> will start services in
6452 each of the multi-user state runlevels (2, 3, 4, and 5)
6453 and stop them in the halt runlevel (0), the single-user
6454 runlevel (1) and the reboot runlevel (6). The system
6455 administrator will have the opportunity to customize
6456 runlevels by simply adding, moving, or removing the
6457 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6458 symbolic links are being used, or by modifying
6459 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6464 To get the default behavior for your package, put in your
6465 <prgn>postinst</prgn> script
6466 <example compact="compact">
6467 update-rc.d <var>package</var> defaults
6469 and in your <prgn>postrm</prgn>
6470 <example compact="compact">
6471 if [ "$1" = purge ]; then
6472 update-rc.d <var>package</var> remove
6474 </example>. Note that if your package changes runlevels
6475 or priority, you may have to remove and recreate the links,
6476 since otherwise the old links may persist. Refer to the
6477 documentation of <prgn>update-rc.d</prgn>.
6481 This will use a default sequence number of 20. If it does
6482 not matter when or in which order the <file>init.d</file>
6483 script is run, use this default. If it does, then you
6484 should talk to the maintainer of the <prgn>sysvinit</prgn>
6485 package or post to <tt>debian-devel</tt>, and they will
6486 help you choose a number.
6490 For more information about using <tt>update-rc.d</tt>,
6491 please consult its man page <manref name="update-rc.d"
6497 <heading>Running initscripts</heading>
6499 The program <prgn>invoke-rc.d</prgn> is provided to make
6500 it easier for package maintainers to properly invoke an
6501 initscript, obeying runlevel and other locally-defined
6502 constraints that might limit a package's right to start,
6503 stop and otherwise manage services. This program may be
6504 used by maintainers in their packages' scripts.
6508 The package maintainer scripts must use
6509 <prgn>invoke-rc.d</prgn> to invoke the
6510 <file>/etc/init.d/*</file> initscripts, instead of
6511 calling them directly.
6515 By default, <prgn>invoke-rc.d</prgn> will pass any
6516 action requests (start, stop, reload, restart...) to the
6517 <file>/etc/init.d</file> script, filtering out requests
6518 to start or restart a service out of its intended
6523 Most packages will simply need to change:
6524 <example compact="compact">/etc/init.d/<package>
6525 <action></example> in their <prgn>postinst</prgn>
6526 and <prgn>prerm</prgn> scripts to:
6527 <example compact="compact">
6528 if which invoke-rc.d >/dev/null 2>&1; then
6529 invoke-rc.d <var>package</var> <action>
6531 /etc/init.d/<var>package</var> <action>
6537 A package should register its initscript services using
6538 <prgn>update-rc.d</prgn> before it tries to invoke them
6539 using <prgn>invoke-rc.d</prgn>. Invocation of
6540 unregistered services may fail.
6544 For more information about using
6545 <prgn>invoke-rc.d</prgn>, please consult its man page
6546 <manref name="invoke-rc.d" section="8">.
6552 <heading>Boot-time initialization</heading>
6555 There used to be another directory, <file>/etc/rc.boot</file>,
6556 which contained scripts which were run once per machine
6557 boot. This has been deprecated in favour of links from
6558 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6559 described in <ref id="/etc/init.d">. Packages must not
6560 place files in <file>/etc/rc.boot</file>.
6565 <heading>Example</heading>
6568 An example on which you can base your
6569 <file>/etc/init.d</file> scripts is found in
6570 <file>/etc/init.d/skeleton</file>.
6577 <heading>Console messages from <file>init.d</file> scripts</heading>
6580 This section describes the formats to be used for messages
6581 written to standard output by the <file>/etc/init.d</file>
6582 scripts. The intent is to improve the consistency of
6583 Debian's startup and shutdown look and feel. For this
6584 reason, please look very carefully at the details. We want
6585 the messages to have the same format in terms of wording,
6586 spaces, punctuation and case of letters.
6590 Here is a list of overall rules that should be used for
6591 messages generated by <file>/etc/init.d</file> scripts.
6597 The message should fit in one line (fewer than 80
6598 characters), start with a capital letter and end with
6599 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6603 If the script is performing some time consuming task in
6604 the background (not merely starting or stopping a
6605 program, for instance), an ellipsis (three dots:
6606 <tt>...</tt>) should be output to the screen, with no
6607 leading or tailing whitespace or line feeds.
6611 The messages should appear as if the computer is telling
6612 the user what it is doing (politely :-), but should not
6613 mention "it" directly. For example, instead of:
6614 <example compact="compact">
6615 I'm starting network daemons: nfsd mountd.
6617 the message should say
6618 <example compact="compact">
6619 Starting network daemons: nfsd mountd.
6626 <tt>init.d</tt> script should use the following standard
6627 message formats for the situations enumerated below.
6633 <p>When daemons are started</p>
6636 If the script starts one or more daemons, the output
6637 should look like this (a single line, no leading
6639 <example compact="compact">
6640 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6642 The <var>description</var> should describe the
6643 subsystem the daemon or set of daemons are part of,
6644 while <var>daemon-1</var> up to <var>daemon-n</var>
6645 denote each daemon's name (typically the file name of
6650 For example, the output of <file>/etc/init.d/lpd</file>
6652 <example compact="compact">
6653 Starting printer spooler: lpd.
6658 This can be achieved by saying
6659 <example compact="compact">
6660 echo -n "Starting printer spooler: lpd"
6661 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6664 in the script. If there are more than one daemon to
6665 start, the output should look like this:
6666 <example compact="compact">
6667 echo -n "Starting remote file system services:"
6668 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6669 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6670 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6673 This makes it possible for the user to see what is
6674 happening and when the final daemon has been started.
6675 Care should be taken in the placement of white spaces:
6676 in the example above the system administrators can
6677 easily comment out a line if they don't want to start
6678 a specific daemon, while the displayed message still
6684 <p>When a system parameter is being set</p>
6687 If you have to set up different system parameters
6688 during the system boot, you should use this format:
6689 <example compact="compact">
6690 Setting <var>parameter</var> to "<var>value</var>".
6695 You can use a statement such as the following to get
6697 <example compact="compact">
6698 echo "Setting DNS domainname to \"$domainname\"."
6703 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6704 for the left and right quotation marks. A grave accent
6705 (<tt>`</tt>) is not a quote character; neither is an
6706 apostrophe (<tt>'</tt>).
6711 <p>When a daemon is stopped or restarted</p>
6714 When you stop or restart a daemon, you should issue a
6715 message identical to the startup message, except that
6716 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6717 or <tt>Restarting</tt> respectively.
6721 For example, stopping the printer daemon will look like
6723 <example compact="compact">
6724 Stopping printer spooler: lpd.
6730 <p>When something is executed</p>
6733 There are several examples where you have to run a
6734 program at system startup or shutdown to perform a
6735 specific task, for example, setting the system's clock
6736 using <prgn>netdate</prgn> or killing all processes
6737 when the system shuts down. Your message should look
6739 <example compact="compact">
6740 Doing something very useful...done.
6742 You should print the <tt>done.</tt> immediately after
6743 the job has been completed, so that the user is
6744 informed why they have to wait. You can get this
6746 <example compact="compact">
6747 echo -n "Doing something very useful..."
6756 <p>When the configuration is reloaded</p>
6759 When a daemon is forced to reload its configuration
6760 files you should use the following format:
6761 <example compact="compact">
6762 Reloading <var>description</var> configuration...done.
6764 where <var>description</var> is the same as in the
6765 daemon starting message.
6773 <heading>Cron jobs</heading>
6776 Packages must not modify the configuration file
6777 <file>/etc/crontab</file>, and they must not modify the files in
6778 <file>/var/spool/cron/crontabs</file>.</p>
6781 If a package wants to install a job that has to be executed
6782 via cron, it should place a file with the name of the
6783 package in one or more of the following directories:
6784 <example compact="compact">
6790 As these directory names imply, the files within them are
6791 executed on an hourly, daily, weekly, or monthly basis,
6792 respectively. The exact times are listed in
6793 <file>/etc/crontab</file>.</p>
6796 All files installed in any of these directories must be
6797 scripts (e.g., shell scripts or Perl scripts) so that they
6798 can easily be modified by the local system administrator.
6799 In addition, they must be treated as configuration files.
6803 If a certain job has to be executed at some other frequency or
6804 at a specific time, the package should install a file
6805 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6806 same syntax as <file>/etc/crontab</file> and is processed by
6807 <prgn>cron</prgn> automatically. The file must also be
6808 treated as a configuration file. (Note that entries in the
6809 <file>/etc/cron.d</file> directory are not handled by
6810 <prgn>anacron</prgn>. Thus, you should only use this
6811 directory for jobs which may be skipped if the system is not
6814 Unlike <file>crontab</file> files described in the IEEE Std
6815 1003.1-2008 (POSIX.1) available from
6816 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6817 name="The Open Group">, the files in
6818 <file>/etc/cron.d</file> and the file
6819 <file>/etc/crontab</file> have seven fields; namely:
6821 <item>Minute [0,59]</item>
6822 <item>Hour [0,23]</item>
6823 <item>Day of the month [1,31]</item>
6824 <item>Month of the year [1,12]</item>
6825 <item>Day of the week ([0,6] with 0=Sunday)</item>
6826 <item>Username</item>
6827 <item>Command to be run</item>
6829 Ranges of numbers are allowed. Ranges are two numbers
6830 separated with a hyphen. The specified range is inclusive.
6831 Lists are allowed. A list is a set of numbers (or ranges)
6832 separated by commas. Step values can be used in conjunction
6837 The scripts or <tt>crontab</tt> entries in these directories should
6838 check if all necessary programs are installed before they
6839 try to execute them. Otherwise, problems will arise when a
6840 package was removed but not purged since configuration files
6841 are kept on the system in this situation.
6845 Any <tt>cron</tt> daemon must provide
6846 <file>/usr/bin/crontab</file> and support normal
6847 <tt>crontab</tt> entries as specified in POSIX. The daemon
6848 must also support names for days and months, ranges, and
6849 step values. It has to support <file>/etc/crontab</file>,
6850 and correctly execute the scripts in
6851 <file>/etc/cron.d</file>. The daemon must also correctly
6853 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6858 <heading>Menus</heading>
6861 The Debian <tt>menu</tt> package provides a standard
6862 interface between packages providing applications and
6863 <em>menu programs</em> (either X window managers or
6864 text-based menu programs such as <prgn>pdmenu</prgn>).
6868 All packages that provide applications that need not be
6869 passed any special command line arguments for normal
6870 operation should register a menu entry for those
6871 applications, so that users of the <tt>menu</tt> package
6872 will automatically get menu entries in their window
6873 managers, as well in shells like <tt>pdmenu</tt>.
6877 Menu entries should follow the current menu policy.
6881 The menu policy can be found in the <tt>menu-policy</tt>
6882 files in the <tt>debian-policy</tt> package.
6883 It is also available from the Debian web mirrors at
6884 <tt><url name="/doc/packaging-manuals/menu-policy/"
6885 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6889 Please also refer to the <em>Debian Menu System</em>
6890 documentation that comes with the <package>menu</package>
6891 package for information about how to register your
6897 <heading>Multimedia handlers</heading>
6900 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6901 is a mechanism for encoding files and data streams and
6902 providing meta-information about them, in particular their
6903 type (e.g. audio or video) and format (e.g. PNG, HTML,
6908 Registration of MIME type handlers allows programs like mail
6909 user agents and web browsers to invoke these handlers to
6910 view, edit or display MIME types they don't support directly.
6914 Packages which provide the ability to view/show/play,
6915 compose, edit or print MIME types should register themselves
6916 as such following the current MIME support policy.
6920 The MIME support policy can be found in the <tt>mime-policy</tt>
6921 files in the <tt>debian-policy</tt> package.
6922 It is also available from the Debian web mirrors at
6923 <tt><url name="/doc/packaging-manuals/mime-policy/"
6924 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6930 <heading>Keyboard configuration</heading>
6933 To achieve a consistent keyboard configuration so that all
6934 applications interpret a keyboard event the same way, all
6935 programs in the Debian distribution must be configured to
6936 comply with the following guidelines.
6940 The following keys must have the specified interpretations:
6943 <tag><tt><--</tt></tag>
6944 <item>delete the character to the left of the cursor</item>
6946 <tag><tt>Delete</tt></tag>
6947 <item>delete the character to the right of the cursor</item>
6949 <tag><tt>Control+H</tt></tag>
6950 <item>emacs: the help prefix</item>
6953 The interpretation of any keyboard events should be
6954 independent of the terminal that is used, be it a virtual
6955 console, an X terminal emulator, an rlogin/telnet session,
6960 The following list explains how the different programs
6961 should be set up to achieve this:
6967 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6971 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6975 X translations are set up to make
6976 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6977 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6978 is the vt220 escape code for the "delete character"
6979 key). This must be done by loading the X resources
6980 using <prgn>xrdb</prgn> on all local X displays, not
6981 using the application defaults, so that the
6982 translation resources used correspond to the
6983 <prgn>xmodmap</prgn> settings.
6987 The Linux console is configured to make
6988 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6989 generate <tt>ESC [ 3 ~</tt>.
6993 X applications are configured so that <tt><</tt>
6994 deletes left, and <tt>Delete</tt> deletes right. Motif
6995 applications already work like this.
6999 Terminals should have <tt>stty erase ^?</tt> .
7003 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7004 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7005 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7009 Emacs is programmed to map <tt>KB_Backspace</tt> or
7010 the <tt>stty erase</tt> character to
7011 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7012 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7013 <tt>^H</tt> to <tt>help</tt> as always.
7017 Other applications use the <tt>stty erase</tt>
7018 character and <tt>kdch1</tt> for the two delete keys,
7019 with ASCII DEL being "delete previous character" and
7020 <tt>kdch1</tt> being "delete character under
7028 This will solve the problem except for the following
7035 Some terminals have a <tt><--</tt> key that cannot
7036 be made to produce anything except <tt>^H</tt>. On
7037 these terminals Emacs help will be unavailable on
7038 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7039 character takes precedence in Emacs, and has been set
7040 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7041 available) can be used instead.
7045 Some operating systems use <tt>^H</tt> for <tt>stty
7046 erase</tt>. However, modern telnet versions and all
7047 rlogin versions propagate <tt>stty</tt> settings, and
7048 almost all UNIX versions honour <tt>stty erase</tt>.
7049 Where the <tt>stty</tt> settings are not propagated
7050 correctly, things can be made to work by using
7051 <tt>stty</tt> manually.
7055 Some systems (including previous Debian versions) use
7056 <prgn>xmodmap</prgn> to arrange for both
7057 <tt><--</tt> and <tt>Delete</tt> to generate
7058 <tt>KB_Delete</tt>. We can change the behavior of
7059 their X clients using the same X resources that we use
7060 to do it for our own clients, or configure our clients
7061 using their resources when things are the other way
7062 around. On displays configured like this
7063 <tt>Delete</tt> will not work, but <tt><--</tt>
7068 Some operating systems have different <tt>kdch1</tt>
7069 settings in their <tt>terminfo</tt> database for
7070 <tt>xterm</tt> and others. On these systems the
7071 <tt>Delete</tt> key will not work correctly when you
7072 log in from a system conforming to our policy, but
7073 <tt><--</tt> will.
7080 <heading>Environment variables</heading>
7083 A program must not depend on environment variables to get
7084 reasonable defaults. (That's because these environment
7085 variables would have to be set in a system-wide
7086 configuration file like <file>/etc/profile</file>, which is not
7087 supported by all shells.)
7091 If a program usually depends on environment variables for its
7092 configuration, the program should be changed to fall back to
7093 a reasonable default configuration if these environment
7094 variables are not present. If this cannot be done easily
7095 (e.g., if the source code of a non-free program is not
7096 available), the program must be replaced by a small
7097 "wrapper" shell script which sets the environment variables
7098 if they are not already defined, and calls the original program.
7102 Here is an example of a wrapper script for this purpose:
7104 <example compact="compact">
7106 BAR=${BAR:-/var/lib/fubar}
7108 exec /usr/lib/foo/foo "$@"
7113 Furthermore, as <file>/etc/profile</file> is a configuration
7114 file of the <prgn>base-files</prgn> package, other packages must
7115 not put any environment variables or other commands into that
7120 <sect id="doc-base">
7121 <heading>Registering Documents using doc-base</heading>
7124 The <package>doc-base</package> package implements a
7125 flexible mechanism for handling and presenting
7126 documentation. The recommended practice is for every Debian
7127 package that provides online documentation (other than just
7128 manual pages) to register these documents with
7129 <package>doc-base</package> by installing a
7130 <package>doc-base</package> control file via the
7131 <prgn/install-docs/ script at installation time and
7132 de-register the manuals again when the package is removed.
7135 Please refer to the documentation that comes with the
7136 <package>doc-base</package> package for information and
7145 <heading>Files</heading>
7147 <sect id="binaries">
7148 <heading>Binaries</heading>
7151 Two different packages must not install programs with
7152 different functionality but with the same filenames. (The
7153 case of two programs having the same functionality but
7154 different implementations is handled via "alternatives" or
7155 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7156 <ref id="conflicts"> respectively.) If this case happens,
7157 one of the programs must be renamed. The maintainers should
7158 report this to the <tt>debian-devel</tt> mailing list and
7159 try to find a consensus about which program will have to be
7160 renamed. If a consensus cannot be reached, <em>both</em>
7161 programs must be renamed.
7165 By default, when a package is being built, any binaries
7166 created should include debugging information, as well as
7167 being compiled with optimization. You should also turn on
7168 as many reasonable compilation warnings as possible; this
7169 makes life easier for porters, who can then look at build
7170 logs for possible problems. For the C programming language,
7171 this means the following compilation parameters should be
7173 <example compact="compact">
7175 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7177 INSTALL = install -s # (or use strip on the files in debian/tmp)
7182 Note that by default all installed binaries should be stripped,
7183 either by using the <tt>-s</tt> flag to
7184 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7185 the binaries after they have been copied into
7186 <file>debian/tmp</file> but before the tree is made into a
7191 Although binaries in the build tree should be compiled with
7192 debugging information by default, it can often be difficult to
7193 debug programs if they are also subjected to compiler
7194 optimization. For this reason, it is recommended to support the
7195 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7196 (see <ref id="debianrules-options">). This variable can contain
7197 several flags to change how a package is compiled and built.
7201 It is up to the package maintainer to decide what
7202 compilation options are best for the package. Certain
7203 binaries (such as computationally-intensive programs) will
7204 function better with certain flags (<tt>-O3</tt>, for
7205 example); feel free to use them. Please use good judgment
7206 here. Don't use flags for the sake of it; only use them
7207 if there is good reason to do so. Feel free to override
7208 the upstream author's ideas about which compilation
7209 options are best: they are often inappropriate for our
7215 <sect id="libraries">
7216 <heading>Libraries</heading>
7219 If the package is <strong>architecture: any</strong>, then
7220 the shared library compilation and linking flags must have
7221 <tt>-fPIC</tt>, or the package shall not build on some of
7222 the supported architectures<footnote>
7224 If you are using GCC, <tt>-fPIC</tt> produces code with
7225 relocatable position independent code, which is required for
7226 most architectures to create a shared library, with i386 and
7227 perhaps some others where non position independent code is
7228 permitted in a shared library.
7231 Position independent code may have a performance penalty,
7232 especially on <tt>i386</tt>. However, in most cases the
7233 speed penalty must be measured against the memory wasted on
7234 the few architectures where non position independent code is
7237 </footnote>. Any exception to this rule must be discussed on
7238 the mailing list <em>debian-devel@lists.debian.org</em>, and
7239 a rough consensus obtained. The reasons for not compiling
7240 with <tt>-fPIC</tt> flag must be recorded in the file
7241 <tt>README.Debian</tt>, and care must be taken to either
7242 restrict the architecture or arrange for <tt>-fPIC</tt> to
7243 be used on architectures where it is required.<footnote>
7245 Some of the reasons why this might be required is if the
7246 library contains hand crafted assembly code that is not
7247 relocatable, the speed penalty is excessive for compute
7248 intensive libs, and similar reasons.
7253 As to the static libraries, the common case is not to have
7254 relocatable code, since there is no benefit, unless in specific
7255 cases; therefore the static version must not be compiled
7256 with the <tt>-fPIC</tt> flag. Any exception to this rule
7257 should be discussed on the mailing list
7258 <em>debian-devel@lists.debian.org</em>, and the reasons for
7259 compiling with the <tt>-fPIC</tt> flag must be recorded in
7260 the file <tt>README.Debian</tt>. <footnote>
7262 Some of the reasons for linking static libraries with
7263 the <tt>-fPIC</tt> flag are if, for example, one needs a
7264 Perl API for a library that is under rapid development,
7265 and has an unstable API, so shared libraries are
7266 pointless at this phase of the library's development. In
7267 that case, since Perl needs a library with relocatable
7268 code, it may make sense to create a static library with
7269 relocatable code. Another reason cited is if you are
7270 distilling various libraries into a common shared
7271 library, like <tt>mklibs</tt> does in the Debian
7277 In other words, if both a shared and a static library is
7278 being built, each source unit (<tt>*.c</tt>, for example,
7279 for C files) will need to be compiled twice, for the normal
7284 Libraries should be built with threading support and to be
7285 thread-safe if the library supports this.
7289 Although not enforced by the build tools, shared libraries
7290 must be linked against all libraries that they use symbols from
7291 in the same way that binaries are. This ensures the correct
7292 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7293 system and guarantees that all libraries can be safely opened
7294 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7295 option <tt>-Wl,-z,defs</tt> when building a shared library.
7296 Since this option enforces symbol resolution at build time,
7297 a missing library reference will be caught early as a fatal
7302 All installed shared libraries should be stripped with
7303 <example compact="compact">
7304 strip --strip-unneeded <var>your-lib</var>
7306 (The option <tt>--strip-unneeded</tt> makes
7307 <prgn>strip</prgn> remove only the symbols which aren't
7308 needed for relocation processing.) Shared libraries can
7309 function perfectly well when stripped, since the symbols for
7310 dynamic linking are in a separate part of the ELF object
7312 You might also want to use the options
7313 <tt>--remove-section=.comment</tt> and
7314 <tt>--remove-section=.note</tt> on both shared libraries
7315 and executables, and <tt>--strip-debug</tt> on static
7321 Note that under some circumstances it may be useful to
7322 install a shared library unstripped, for example when
7323 building a separate package to support debugging.
7327 Shared object files (often <file>.so</file> files) that are not
7328 public libraries, that is, they are not meant to be linked
7329 to by third party executables (binaries of other packages),
7330 should be installed in subdirectories of the
7331 <file>/usr/lib</file> directory. Such files are exempt from the
7332 rules that govern ordinary shared libraries, except that
7333 they must not be installed executable and should be
7335 A common example are the so-called "plug-ins",
7336 internal shared objects that are dynamically loaded by
7337 programs using <manref name="dlopen" section="3">.
7342 Packages that use <prgn>libtool</prgn> to create and install
7343 their shared libraries install a file containing additional
7344 metadata (ending in <file>.la</file>) alongside the library.
7345 For public libraries intended for use by other packages, these
7346 files normally should not be included in the Debian package,
7347 since the information they include is not necessary to link with
7348 the shared library on Debian and can add unnecessary additional
7349 dependencies to other programs or libraries.<footnote>
7350 These files store, among other things, all libraries on which
7351 that shared library depends. Unfortunately, if
7352 the <file>.la</file> file is present and contains that
7353 dependency information, using <prgn>libtool</prgn> when
7354 linking against that library will cause the resulting program
7355 or library to be linked against those dependencies as well,
7356 even if this is unnecessary. This can create unneeded
7357 dependencies on shared library packages that would otherwise
7358 be hidden behind the library ABI, and can make library
7359 transitions to new SONAMEs unnecessarily complicated and
7360 difficult to manage.
7362 If the <file>.la</file> file is required for that library (if,
7363 for instance, it's loaded via <tt>libltdl</tt> in a way that
7364 requires that meta-information), the <tt>dependency_libs</tt>
7365 setting in the <file>.la</file> file should normally be set to
7366 the empty string. If the shared library development package has
7367 historically included the <file>.la</file>, it must be retained
7368 in the development package (with <tt>dependency_libs</tt>
7369 emptied) until all libraries that depend on it have removed or
7370 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7371 files to prevent linking with those other libraries
7372 using <prgn>libtool</prgn> from failing.
7376 If the <file>.la</file> must be included, it should be included
7377 in the development (<tt>-dev</tt>) package, unless the library
7378 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7379 library. If it is intended for use with <tt>libltdl</tt>,
7380 the <file>.la</file> files must go in the run-time library
7385 These requirements for handling of <file>.la</file> files do not
7386 apply to loadable modules or libraries not installed in
7387 directories searched by default by the dynamic linker. Packages
7388 installing loadable modules will frequently need to install
7389 the <file>.la</file> files alongside the modules so that they
7390 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7391 does not need to be modified for libraries or modules that are
7392 not installed in directories searched by the dynamic linker by
7393 default and not intended for use by other packages.
7397 You must make sure that you use only released versions of
7398 shared libraries to build your packages; otherwise other
7399 users will not be able to run your binaries
7400 properly. Producing source packages that depend on
7401 unreleased compilers is also usually a bad
7408 <heading>Shared libraries</heading>
7410 This section has moved to <ref id="sharedlibs">.
7416 <heading>Scripts</heading>
7419 All command scripts, including the package maintainer
7420 scripts inside the package and used by <prgn>dpkg</prgn>,
7421 should have a <tt>#!</tt> line naming the shell to be used
7426 In the case of Perl scripts this should be
7427 <tt>#!/usr/bin/perl</tt>.
7431 When scripts are installed into a directory in the system
7432 PATH, the script name should not include an extension such
7433 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7434 language currently used to implement it.
7437 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7438 <file>init.d</file> scripts should almost certainly start
7439 with <tt>set -e</tt> so that errors are detected.
7440 <file>init.d</file> scripts are something of a special case, due
7441 to how frequently they need to call commands that are allowed to
7442 fail, and it may instead be easier to check the exit status of
7443 commands directly. See <ref id="writing-init"> for more
7444 information about writing <file>init.d</file> scripts.
7447 Every script should use <tt>set -e</tt> or check the exit status
7448 of <em>every</em> command.
7451 Scripts may assume that <file>/bin/sh</file> implements the
7452 SUSv3 Shell Command Language<footnote>
7453 Single UNIX Specification, version 3, which is also IEEE
7454 1003.1-2004 (POSIX), and is available on the World Wide Web
7455 from <url id="http://www.unix.org/version3/online.html"
7456 name="The Open Group"> after free
7457 registration.</footnote>
7458 plus the following additional features not mandated by
7460 These features are in widespread use in the Linux community
7461 and are implemented in all of bash, dash, and ksh, the most
7462 common shells users may wish to use as <file>/bin/sh</file>.
7465 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7466 must not generate a newline.</item>
7467 <item><tt>test</tt>, if implemented as a shell built-in, must
7468 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7470 <item><tt>local</tt> to create a scoped variable must be
7471 supported, including listing multiple variables in a single
7472 local command and assigning a value to a variable at the
7473 same time as localizing it. <tt>local</tt> may or
7474 may not preserve the variable value from an outer scope if
7475 no assignment is present. Uses such as:
7479 # ... use a, b, c, d ...
7482 must be supported and must set the value of <tt>c</tt> to
7486 If a shell script requires non-SUSv3 features from the shell
7487 interpreter other than those listed above, the appropriate shell
7488 must be specified in the first line of the script (e.g.,
7489 <tt>#!/bin/bash</tt>) and the package must depend on the package
7490 providing the shell (unless the shell package is marked
7491 "Essential", as in the case of <prgn>bash</prgn>).
7495 You may wish to restrict your script to SUSv3 features plus the
7496 above set when possible so that it may use <file>/bin/sh</file>
7497 as its interpreter. If your script works with <prgn>dash</prgn>
7498 (originally called <prgn>ash</prgn>), it probably complies with
7499 the above requirements, but if you are in doubt, use
7500 <file>/bin/bash</file>.
7504 Perl scripts should check for errors when making any
7505 system calls, including <tt>open</tt>, <tt>print</tt>,
7506 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7510 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7511 scripting languages. See <em>Csh Programming Considered
7512 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7513 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7514 If an upstream package comes with <prgn>csh</prgn> scripts
7515 then you must make sure that they start with
7516 <tt>#!/bin/csh</tt> and make your package depend on the
7517 <prgn>c-shell</prgn> virtual package.
7521 Any scripts which create files in world-writeable
7522 directories (e.g., in <file>/tmp</file>) must use a
7523 mechanism which will fail atomically if a file with the same
7524 name already exists.
7528 The Debian base system provides the <prgn>tempfile</prgn>
7529 and <prgn>mktemp</prgn> utilities for use by scripts for
7536 <heading>Symbolic links</heading>
7539 In general, symbolic links within a top-level directory
7540 should be relative, and symbolic links pointing from one
7541 top-level directory into another should be absolute. (A
7542 top-level directory is a sub-directory of the root
7543 directory <file>/</file>.)
7547 In addition, symbolic links should be specified as short as
7548 possible, i.e., link targets like <file>foo/../bar</file> are
7553 Note that when creating a relative link using
7554 <prgn>ln</prgn> it is not necessary for the target of the
7555 link to exist relative to the working directory you're
7556 running <prgn>ln</prgn> from, nor is it necessary to change
7557 directory to the directory where the link is to be made.
7558 Simply include the string that should appear as the target
7559 of the link (this will be a pathname relative to the
7560 directory in which the link resides) as the first argument
7565 For example, in your <prgn>Makefile</prgn> or
7566 <file>debian/rules</file>, you can do things like:
7567 <example compact="compact">
7568 ln -fs gcc $(prefix)/bin/cc
7569 ln -fs gcc debian/tmp/usr/bin/cc
7570 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7571 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7576 A symbolic link pointing to a compressed file should always
7577 have the same file extension as the referenced file. (For
7578 example, if a file <file>foo.gz</file> is referenced by a
7579 symbolic link, the filename of the link has to end with
7580 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7585 <heading>Device files</heading>
7588 Packages must not include device files or named pipes in the
7593 If a package needs any special device files that are not
7594 included in the base system, it must call
7595 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7596 after notifying the user<footnote>
7597 This notification could be done via a (low-priority)
7598 debconf message, or an echo (printf) statement.
7603 Packages must not remove any device files in the
7604 <prgn>postrm</prgn> or any other script. This is left to the
7605 system administrator.
7609 Debian uses the serial devices
7610 <file>/dev/ttyS*</file>. Programs using the old
7611 <file>/dev/cu*</file> devices should be changed to use
7612 <file>/dev/ttyS*</file>.
7616 Named pipes needed by the package must be created in
7617 the <prgn>postinst</prgn> script<footnote>
7618 It's better to use <prgn>mkfifo</prgn> rather
7619 than <prgn>mknod</prgn> to create named pipes so that
7620 automated checks for packages incorrectly creating device
7621 files with <prgn>mknod</prgn> won't have false positives.
7622 </footnote> and removed in
7623 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7628 <sect id="config-files">
7629 <heading>Configuration files</heading>
7632 <heading>Definitions</heading>
7636 <tag>configuration file</tag>
7638 A file that affects the operation of a program, or
7639 provides site- or host-specific information, or
7640 otherwise customizes the behavior of a program.
7641 Typically, configuration files are intended to be
7642 modified by the system administrator (if needed or
7643 desired) to conform to local policy or to provide
7644 more useful site-specific behavior.
7647 <tag><tt>conffile</tt></tag>
7649 A file listed in a package's <tt>conffiles</tt>
7650 file, and is treated specially by <prgn>dpkg</prgn>
7651 (see <ref id="configdetails">).
7657 The distinction between these two is important; they are
7658 not interchangeable concepts. Almost all
7659 <tt>conffile</tt>s are configuration files, but many
7660 configuration files are not <tt>conffiles</tt>.
7664 As noted elsewhere, <file>/etc/init.d</file> scripts,
7665 <file>/etc/default</file> files, scripts installed in
7666 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7667 configuration installed in <file>/etc/cron.d</file> must be
7668 treated as configuration files. In general, any script that
7669 embeds configuration information is de-facto a configuration
7670 file and should be treated as such.
7675 <heading>Location</heading>
7678 Any configuration files created or used by your package
7679 must reside in <file>/etc</file>. If there are several,
7680 consider creating a subdirectory of <file>/etc</file>
7681 named after your package.
7685 If your package creates or uses configuration files
7686 outside of <file>/etc</file>, and it is not feasible to modify
7687 the package to use <file>/etc</file> directly, put the files
7688 in <file>/etc</file> and create symbolic links to those files
7689 from the location that the package requires.
7694 <heading>Behavior</heading>
7697 Configuration file handling must conform to the following
7699 <list compact="compact">
7701 local changes must be preserved during a package
7705 configuration files must be preserved when the
7706 package is removed, and only deleted when the
7710 Obsolete configuration files without local changes may be
7711 removed by the package during upgrade.
7715 The easy way to achieve this behavior is to make the
7716 configuration file a <tt>conffile</tt>. This is
7717 appropriate only if it is possible to distribute a default
7718 version that will work for most installations, although
7719 some system administrators may choose to modify it. This
7720 implies that the default version will be part of the
7721 package distribution, and must not be modified by the
7722 maintainer scripts during installation (or at any other
7727 In order to ensure that local changes are preserved
7728 correctly, no package may contain or make hard links to
7729 conffiles.<footnote>
7730 Rationale: There are two problems with hard links.
7731 The first is that some editors break the link while
7732 editing one of the files, so that the two files may
7733 unwittingly become unlinked and different. The second
7734 is that <prgn>dpkg</prgn> might break the hard link
7735 while upgrading <tt>conffile</tt>s.
7740 The other way to do it is via the maintainer scripts. In
7741 this case, the configuration file must not be listed as a
7742 <tt>conffile</tt> and must not be part of the package
7743 distribution. If the existence of a file is required for
7744 the package to be sensibly configured it is the
7745 responsibility of the package maintainer to provide
7746 maintainer scripts which correctly create, update and
7747 maintain the file and remove it on purge. (See <ref
7748 id="maintainerscripts"> for more information.) These
7749 scripts must be idempotent (i.e., must work correctly if
7750 <prgn>dpkg</prgn> needs to re-run them due to errors
7751 during installation or removal), must cope with all the
7752 variety of ways <prgn>dpkg</prgn> can call maintainer
7753 scripts, must not overwrite or otherwise mangle the user's
7754 configuration without asking, must not ask unnecessary
7755 questions (particularly during upgrades), and must
7756 otherwise be good citizens.
7760 The scripts are not required to configure every possible
7761 option for the package, but only those necessary to get
7762 the package running on a given system. Ideally the
7763 sysadmin should not have to do any configuration other
7764 than that done (semi-)automatically by the
7765 <prgn>postinst</prgn> script.
7769 A common practice is to create a script called
7770 <file><var>package</var>-configure</file> and have the
7771 package's <prgn>postinst</prgn> call it if and only if the
7772 configuration file does not already exist. In certain
7773 cases it is useful for there to be an example or template
7774 file which the maintainer scripts use. Such files should
7775 be in <file>/usr/share/<var>package</var></file> or
7776 <file>/usr/lib/<var>package</var></file> (depending on whether
7777 they are architecture-independent or not). There should
7778 be symbolic links to them from
7779 <file>/usr/share/doc/<var>package</var>/examples</file> if
7780 they are examples, and should be perfectly ordinary
7781 <prgn>dpkg</prgn>-handled files (<em>not</em>
7782 configuration files).
7786 These two styles of configuration file handling must
7787 not be mixed, for that way lies madness:
7788 <prgn>dpkg</prgn> will ask about overwriting the file
7789 every time the package is upgraded.
7794 <heading>Sharing configuration files</heading>
7797 Packages which specify the same file as a
7798 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7799 with each other. (This is an instance of the general rule
7800 about not sharing files. Note that neither alternatives
7801 nor diversions are likely to be appropriate in this case;
7802 in particular, <prgn>dpkg</prgn> does not handle diverted
7803 <tt>conffile</tt>s well.)
7807 The maintainer scripts must not alter a <tt>conffile</tt>
7808 of <em>any</em> package, including the one the scripts
7813 If two or more packages use the same configuration file
7814 and it is reasonable for both to be installed at the same
7815 time, one of these packages must be defined as
7816 <em>owner</em> of the configuration file, i.e., it will be
7817 the package which handles that file as a configuration
7818 file. Other packages that use the configuration file must
7819 depend on the owning package if they require the
7820 configuration file to operate. If the other package will
7821 use the configuration file if present, but is capable of
7822 operating without it, no dependency need be declared.
7826 If it is desirable for two or more related packages to
7827 share a configuration file <em>and</em> for all of the
7828 related packages to be able to modify that configuration
7829 file, then the following should be done:
7830 <enumlist compact="compact">
7832 One of the related packages (the "owning" package)
7833 will manage the configuration file with maintainer
7834 scripts as described in the previous section.
7837 The owning package should also provide a program
7838 that the other packages may use to modify the
7842 The related packages must use the provided program
7843 to make any desired modifications to the
7844 configuration file. They should either depend on
7845 the core package to guarantee that the configuration
7846 modifier program is available or accept gracefully
7847 that they cannot modify the configuration file if it
7848 is not. (This is in addition to the fact that the
7849 configuration file may not even be present in the
7856 Sometimes it's appropriate to create a new package which
7857 provides the basic infrastructure for the other packages
7858 and which manages the shared configuration files. (The
7859 <tt>sgml-base</tt> package is a good example.)
7864 <heading>User configuration files ("dotfiles")</heading>
7867 The files in <file>/etc/skel</file> will automatically be
7868 copied into new user accounts by <prgn>adduser</prgn>.
7869 No other program should reference the files in
7870 <file>/etc/skel</file>.
7874 Therefore, if a program needs a dotfile to exist in
7875 advance in <file>$HOME</file> to work sensibly, that dotfile
7876 should be installed in <file>/etc/skel</file> and treated as a
7881 However, programs that require dotfiles in order to
7882 operate sensibly are a bad thing, unless they do create
7883 the dotfiles themselves automatically.
7887 Furthermore, programs should be configured by the Debian
7888 default installation to behave as closely to the upstream
7889 default behavior as possible.
7893 Therefore, if a program in a Debian package needs to be
7894 configured in some way in order to operate sensibly, that
7895 should be done using a site-wide configuration file placed
7896 in <file>/etc</file>. Only if the program doesn't support a
7897 site-wide default configuration and the package maintainer
7898 doesn't have time to add it may a default per-user file be
7899 placed in <file>/etc/skel</file>.
7903 <file>/etc/skel</file> should be as empty as we can make it.
7904 This is particularly true because there is no easy (or
7905 necessarily desirable) mechanism for ensuring that the
7906 appropriate dotfiles are copied into the accounts of
7907 existing users when a package is installed.
7913 <heading>Log files</heading>
7915 Log files should usually be named
7916 <file>/var/log/<var>package</var>.log</file>. If you have many
7917 log files, or need a separate directory for permission
7918 reasons (<file>/var/log</file> is writable only by
7919 <file>root</file>), you should usually create a directory named
7920 <file>/var/log/<var>package</var></file> and place your log
7925 Log files must be rotated occasionally so that they don't
7926 grow indefinitely; the best way to do this is to drop a log
7927 rotation configuration file into the directory
7928 <file>/etc/logrotate.d</file> and use the facilities provided by
7929 logrotate.<footnote>
7931 The traditional approach to log files has been to set up
7932 <em>ad hoc</em> log rotation schemes using simple shell
7933 scripts and cron. While this approach is highly
7934 customizable, it requires quite a lot of sysadmin work.
7935 Even though the original Debian system helped a little
7936 by automatically installing a system which can be used
7937 as a template, this was deemed not enough.
7941 The use of <prgn>logrotate</prgn>, a program developed
7942 by Red Hat, is better, as it centralizes log management.
7943 It has both a configuration file
7944 (<file>/etc/logrotate.conf</file>) and a directory where
7945 packages can drop their individual log rotation
7946 configurations (<file>/etc/logrotate.d</file>).
7949 Here is a good example for a logrotate config
7950 file (for more information see <manref name="logrotate"
7952 <example compact="compact">
7953 /var/log/foo/*.log {
7958 /etc/init.d/foo force-reload
7962 This rotates all files under <file>/var/log/foo</file>, saves 12
7963 compressed generations, and forces the daemon to reload its
7964 configuration information after the log rotation.
7968 Log files should be removed when the package is
7969 purged (but not when it is only removed). This should be
7970 done by the <prgn>postrm</prgn> script when it is called
7971 with the argument <tt>purge</tt> (see <ref
7972 id="removedetails">).
7977 <heading>Permissions and owners</heading>
7980 The rules in this section are guidelines for general use.
7981 If necessary you may deviate from the details below.
7982 However, if you do so you must make sure that what is done
7983 is secure and you should try to be as consistent as possible
7984 with the rest of the system. You should probably also
7985 discuss it on <prgn>debian-devel</prgn> first.
7989 Files should be owned by <tt>root:root</tt>, and made
7990 writable only by the owner and universally readable (and
7991 executable, if appropriate), that is mode 644 or 755.
7995 Directories should be mode 755 or (for group-writability)
7996 mode 2775. The ownership of the directory should be
7997 consistent with its mode: if a directory is mode 2775, it
7998 should be owned by the group that needs write access to
8001 When a package is upgraded, and the owner or permissions
8002 of a file included in the package has changed, dpkg
8003 arranges for the ownership and permissions to be
8004 correctly set upon installation. However, this does not
8005 extend to directories; the permissions and ownership of
8006 directories already on the system does not change on
8007 install or upgrade of packages. This makes sense, since
8008 otherwise common directories like <tt>/usr</tt> would
8009 always be in flux. To correctly change permissions of a
8010 directory the package owns, explicit action is required,
8011 usually in the <tt>postinst</tt> script. Care must be
8012 taken to handle downgrades as well, in that case.
8019 Setuid and setgid executables should be mode 4755 or 2755
8020 respectively, and owned by the appropriate user or group.
8021 They should not be made unreadable (modes like 4711 or
8022 2711 or even 4111); doing so achieves no extra security,
8023 because anyone can find the binary in the freely available
8024 Debian package; it is merely inconvenient. For the same
8025 reason you should not restrict read or execute permissions
8026 on non-set-id executables.
8030 Some setuid programs need to be restricted to particular
8031 sets of users, using file permissions. In this case they
8032 should be owned by the uid to which they are set-id, and by
8033 the group which should be allowed to execute them. They
8034 should have mode 4754; again there is no point in making
8035 them unreadable to those users who must not be allowed to
8040 It is possible to arrange that the system administrator can
8041 reconfigure the package to correspond to their local
8042 security policy by changing the permissions on a binary:
8043 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8044 described below.<footnote>
8045 Ordinary files installed by <prgn>dpkg</prgn> (as
8046 opposed to <tt>conffile</tt>s and other similar objects)
8047 normally have their permissions reset to the distributed
8048 permissions when the package is reinstalled. However,
8049 the use of <prgn>dpkg-statoverride</prgn> overrides this
8052 Another method you should consider is to create a group for
8053 people allowed to use the program(s) and make any setuid
8054 executables executable only by that group.
8058 If you need to create a new user or group for your package
8059 there are two possibilities. Firstly, you may need to
8060 make some files in the binary package be owned by this
8061 user or group, or you may need to compile the user or
8062 group id (rather than just the name) into the binary
8063 (though this latter should be avoided if possible, as in
8064 this case you need a statically allocated id).</p>
8067 If you need a statically allocated id, you must ask for a
8068 user or group id from the <tt>base-passwd</tt> maintainer,
8069 and must not release the package until you have been
8070 allocated one. Once you have been allocated one you must
8071 either make the package depend on a version of the
8072 <tt>base-passwd</tt> package with the id present in
8073 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8074 your package to create the user or group itself with the
8075 correct id (using <tt>adduser</tt>) in its
8076 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8077 the <prgn>postinst</prgn> is to be preferred if it is
8078 possible, otherwise a pre-dependency will be needed on the
8079 <tt>adduser</tt> package.)
8083 On the other hand, the program might be able to determine
8084 the uid or gid from the user or group name at runtime, so
8085 that a dynamically allocated id can be used. In this case
8086 you should choose an appropriate user or group name,
8087 discussing this on <prgn>debian-devel</prgn> and checking
8088 with the <package/base-passwd/ maintainer that it is unique and that
8089 they do not wish you to use a statically allocated id
8090 instead. When this has been checked you must arrange for
8091 your package to create the user or group if necessary using
8092 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8093 <prgn>postinst</prgn> script (again, the latter is to be
8094 preferred if it is possible).
8098 Note that changing the numeric value of an id associated
8099 with a name is very difficult, and involves searching the
8100 file system for all appropriate files. You need to think
8101 carefully whether a static or dynamic id is required, since
8102 changing your mind later will cause problems.
8105 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8107 This section is not intended as policy, but as a
8108 description of the use of <prgn>dpkg-statoverride</prgn>.
8112 If a system administrator wishes to have a file (or
8113 directory or other such thing) installed with owner and
8114 permissions different from those in the distributed Debian
8115 package, they can use the <prgn>dpkg-statoverride</prgn>
8116 program to instruct <prgn>dpkg</prgn> to use the different
8117 settings every time the file is installed. Thus the
8118 package maintainer should distribute the files with their
8119 normal permissions, and leave it for the system
8120 administrator to make any desired changes. For example, a
8121 daemon which is normally required to be setuid root, but
8122 in certain situations could be used without being setuid,
8123 should be installed setuid in the <tt>.deb</tt>. Then the
8124 local system administrator can change this if they wish.
8125 If there are two standard ways of doing it, the package
8126 maintainer can use <tt>debconf</tt> to find out the
8127 preference, and call <prgn>dpkg-statoverride</prgn> in the
8128 maintainer script if necessary to accommodate the system
8129 administrator's choice. Care must be taken during
8130 upgrades to not override an existing setting.
8134 Given the above, <prgn>dpkg-statoverride</prgn> is
8135 essentially a tool for system administrators and would not
8136 normally be needed in the maintainer scripts. There is
8137 one type of situation, though, where calls to
8138 <prgn>dpkg-statoverride</prgn> would be needed in the
8139 maintainer scripts, and that involves packages which use
8140 dynamically allocated user or group ids. In such a
8141 situation, something like the following idiom can be very
8142 helpful in the package's <prgn>postinst</prgn>, where
8143 <tt>sysuser</tt> is a dynamically allocated id:
8145 for i in /usr/bin/foo /usr/sbin/bar
8147 # only do something when no setting exists
8148 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8150 #include: debconf processing, question about foo and bar
8151 if [ "$RET" = "true" ] ; then
8152 dpkg-statoverride --update --add sysuser root 4755 $i
8157 The corresponding code to remove the override when the package
8160 for i in /usr/bin/foo /usr/sbin/bar
8162 if dpkg-statoverride --list $i >/dev/null 2>&1
8164 dpkg-statoverride --remove $i
8174 <chapt id="customized-programs">
8175 <heading>Customized programs</heading>
8177 <sect id="arch-spec">
8178 <heading>Architecture specification strings</heading>
8181 If a program needs to specify an <em>architecture specification
8182 string</em> in some place, it should select one of the strings
8183 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8184 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8185 part is sometimes elided, as when the OS is Linux.
8189 Note that we don't want to use
8190 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8191 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8192 since this would make our programs incompatible with other
8193 Linux distributions. We also don't use something like
8194 <tt><var>arch</var>-unknown-linux</tt>, since the
8195 <tt>unknown</tt> does not look very good.
8198 <sect1 id="arch-wildcard-spec">
8199 <heading>Architecture wildcards</heading>
8202 A package may specify an architecture wildcard. Architecture
8203 wildcards are in the format <tt>any</tt> (which matches every
8204 architecture), <tt><var>os</var></tt>-any, or
8205 any-<tt><var>cpu</var></tt>. <footnote>
8206 Internally, the package system normalizes the GNU triplets
8207 and the Debian arches into Debian arch triplets (which are
8208 kind of inverted GNU triplets), with the first component of
8209 the triplet representing the libc and ABI in use, and then
8210 does matching against those triplets. However, such
8211 triplets are an internal implementation detail that should
8212 not be used by packages directly. The libc and ABI portion
8213 is handled internally by the package system based on
8214 the <var>os</var> and <var>cpu</var>.
8221 <heading>Daemons</heading>
8224 The configuration files <file>/etc/services</file>,
8225 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8226 by the <prgn>netbase</prgn> package and must not be modified
8231 If a package requires a new entry in one of these files, the
8232 maintainer should get in contact with the
8233 <prgn>netbase</prgn> maintainer, who will add the entries
8234 and release a new version of the <prgn>netbase</prgn>
8239 The configuration file <file>/etc/inetd.conf</file> must not be
8240 modified by the package's scripts except via the
8241 <prgn>update-inetd</prgn> script or the
8242 <file>DebianNet.pm</file> Perl module. See their documentation
8243 for details on how to add entries.
8247 If a package wants to install an example entry into
8248 <file>/etc/inetd.conf</file>, the entry must be preceded with
8249 exactly one hash character (<tt>#</tt>). Such lines are
8250 treated as "commented out by user" by the
8251 <prgn>update-inetd</prgn> script and are not changed or
8252 activated during package updates.
8257 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8261 Some programs need to create pseudo-ttys. This should be done
8262 using Unix98 ptys if the C library supports it. The resulting
8263 program must not be installed setuid root, unless that
8264 is required for other functionality.
8268 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8269 <file>/var/log/lastlog</file> must be installed writable by
8270 group <tt>utmp</tt>. Programs which need to modify those
8271 files must be installed setgid <tt>utmp</tt>.
8276 <heading>Editors and pagers</heading>
8279 Some programs have the ability to launch an editor or pager
8280 program to edit or display a text document. Since there are
8281 lots of different editors and pagers available in the Debian
8282 distribution, the system administrator and each user should
8283 have the possibility to choose their preferred editor and
8288 In addition, every program should choose a good default
8289 editor/pager if none is selected by the user or system
8294 Thus, every program that launches an editor or pager must
8295 use the EDITOR or PAGER environment variable to determine
8296 the editor or pager the user wishes to use. If these
8297 variables are not set, the programs <file>/usr/bin/editor</file>
8298 and <file>/usr/bin/pager</file> should be used, respectively.
8302 These two files are managed through the <prgn>dpkg</prgn>
8303 "alternatives" mechanism. Every package providing an editor or
8304 pager must call the <prgn>update-alternatives</prgn> script to
8305 register as an alternative for <file>/usr/bin/editor</file>
8306 or <file>/usr/bin/pager</file> as appropriate. The alternative
8307 should have a slave alternative
8308 for <file>/usr/share/man/man1/editor.1.gz</file>
8309 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8310 corresponding manual page.
8314 If it is very hard to adapt a program to make use of the
8315 EDITOR or PAGER variables, that program may be configured to
8316 use <file>/usr/bin/sensible-editor</file> and
8317 <file>/usr/bin/sensible-pager</file> as the editor or pager
8318 program respectively. These are two scripts provided in the
8319 <package>sensible-utils</package> package that check the EDITOR
8320 and PAGER variables and launch the appropriate program, and fall
8321 back to <file>/usr/bin/editor</file>
8322 and <file>/usr/bin/pager</file> if the variable is not set.
8326 A program may also use the VISUAL environment variable to
8327 determine the user's choice of editor. If it exists, it
8328 should take precedence over EDITOR. This is in fact what
8329 <file>/usr/bin/sensible-editor</file> does.
8333 It is not required for a package to depend on
8334 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8335 package to provide such virtual packages.<footnote>
8336 The Debian base system already provides an editor and a
8342 <sect id="web-appl">
8343 <heading>Web servers and applications</heading>
8346 This section describes the locations and URLs that should
8347 be used by all web servers and web applications in the
8354 Cgi-bin executable files are installed in the
8356 <example compact="compact">
8357 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8359 or a subdirectory of that directory, and should be
8361 <example compact="compact">
8362 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8364 (possibly with a subdirectory name
8365 before <var>cgi-bin-name</var>).
8369 <p>Access to HTML documents</p>
8372 HTML documents for a package are stored in
8373 <file>/usr/share/doc/<var>package</var></file>
8374 and can be referred to as
8375 <example compact="compact">
8376 http://localhost/doc/<var>package</var>/<var>filename</var>
8381 The web server should restrict access to the document
8382 tree so that only clients on the same host can read
8383 the documents. If the web server does not support such
8384 access controls, then it should not provide access at
8385 all, or ask about providing access during installation.
8390 <p>Access to images</p>
8392 It is recommended that images for a package be stored
8393 in <tt>/usr/share/images/<var>package</var></tt> and
8394 may be referred to through an alias <tt>/images/</tt>
8397 http://localhost/images/<package>/<filename>
8404 <p>Web Document Root</p>
8407 Web Applications should try to avoid storing files in
8408 the Web Document Root. Instead they should use the
8409 /usr/share/doc/<var>package</var> directory for
8410 documents and register the Web Application via the
8411 <package>doc-base</package> package. If access to the
8412 web document root is unavoidable then use
8413 <example compact="compact">
8416 as the Document Root. This might be just a symbolic
8417 link to the location where the system administrator
8418 has put the real document root.
8421 <item><p>Providing httpd and/or httpd-cgi</p>
8423 All web servers should provide the virtual package
8424 <tt>httpd</tt>. If a web server has CGI support it should
8425 provide <tt>httpd-cgi</tt> additionally.
8428 All web applications which do not contain CGI scripts should
8429 depend on <tt>httpd</tt>, all those web applications which
8430 <tt>do</tt> contain CGI scripts, should depend on
8438 <sect id="mail-transport-agents">
8439 <heading>Mail transport, delivery and user agents</heading>
8442 Debian packages which process electronic mail, whether mail
8443 user agents (MUAs) or mail transport agents (MTAs), must
8444 ensure that they are compatible with the configuration
8445 decisions below. Failure to do this may result in lost
8446 mail, broken <tt>From:</tt> lines, and other serious brain
8451 The mail spool is <file>/var/mail</file> and the interface to
8452 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8453 the FHS). On older systems, the mail spool may be
8454 physically located in <file>/var/spool/mail</file>, but all
8455 access to the mail spool should be via the
8456 <file>/var/mail</file> symlink. The mail spool is part of the
8457 base system and not part of the MTA package.
8461 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8462 programs (such as IMAP daemons) must lock the mailbox in an
8463 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8464 be combined with dot locking. To avoid deadlocks, a program
8465 should use <tt>fcntl()</tt> first and dot locking after
8466 this, or alternatively implement the two locking methods in
8467 a non blocking way<footnote>
8468 If it is not possible to establish both locks, the
8469 system shouldn't wait for the second lock to be
8470 established, but remove the first lock, wait a (random)
8471 time, and start over locking again.
8472 </footnote>. Using the functions <tt>maillock</tt> and
8473 <tt>mailunlock</tt> provided by the
8474 <tt>liblockfile*</tt><footnote>
8475 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8476 to use these functions.
8477 </footnote> packages is the recommended way to realize this.
8481 Mailboxes are generally either mode 600 and owned by
8482 <var>user</var> or mode 660 and owned by
8483 <tt><var>user</var>:mail</tt><footnote>
8484 There are two traditional permission schemes for mail spools:
8485 mode 600 with all mail delivery done by processes running as
8486 the destination user, or mode 660 and owned by group mail with
8487 mail delivery done by a process running as a system user in
8488 group mail. Historically, Debian required mode 660 mail
8489 spools to enable the latter model, but that model has become
8490 increasingly uncommon and the principle of least privilege
8491 indicates that mail systems that use the first model should
8492 use permissions of 600. If delivery to programs is permitted,
8493 it's easier to keep the mail system secure if the delivery
8494 agent runs as the destination user. Debian Policy therefore
8495 permits either scheme.
8496 </footnote>. The local system administrator may choose a
8497 different permission scheme; packages should not make
8498 assumptions about the permission and ownership of mailboxes
8499 unless required (such as when creating a new mailbox). A MUA
8500 may remove a mailbox (unless it has nonstandard permissions) in
8501 which case the MTA or another MUA must recreate it if needed.
8505 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8506 be setgid mail to do the locking mentioned above (and
8507 must obviously avoid accessing other users' mailboxes
8508 using this privilege).</p>
8511 <file>/etc/aliases</file> is the source file for the system mail
8512 aliases (e.g., postmaster, usenet, etc.), it is the one
8513 which the sysadmin and <prgn>postinst</prgn> scripts may
8514 edit. After <file>/etc/aliases</file> is edited the program or
8515 human editing it must call <prgn>newaliases</prgn>. All MTA
8516 packages must come with a <prgn>newaliases</prgn> program,
8517 even if it does nothing, but older MTA packages did not do
8518 this so programs should not fail if <prgn>newaliases</prgn>
8519 cannot be found. Note that because of this, all MTA
8520 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8521 <tt>Replaces: mail-transport-agent</tt> control fields.
8525 The convention of writing <tt>forward to
8526 <var>address</var></tt> in the mailbox itself is not
8527 supported. Use a <tt>.forward</tt> file instead.</p>
8530 The <prgn>rmail</prgn> program used by UUCP
8531 for incoming mail should be <file>/usr/sbin/rmail</file>.
8532 Likewise, <prgn>rsmtp</prgn>, for receiving
8533 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8537 If your package needs to know what hostname to use on (for
8538 example) outgoing news and mail messages which are generated
8539 locally, you should use the file <file>/etc/mailname</file>. It
8540 will contain the portion after the username and <tt>@</tt>
8541 (at) sign for email addresses of users on the machine
8542 (followed by a newline).
8546 Such a package should check for the existence of this file
8547 when it is being configured. If it exists, it should be
8548 used without comment, although an MTA's configuration script
8549 may wish to prompt the user even if it finds that this file
8550 exists. If the file does not exist, the package should
8551 prompt the user for the value (preferably using
8552 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8553 as well as using it in the package's configuration. The
8554 prompt should make it clear that the name will not just be
8555 used by that package. For example, in this situation the
8556 <tt>inn</tt> package could say something like:
8557 <example compact="compact">
8558 Please enter the "mail name" of your system. This is the
8559 hostname portion of the address to be shown on outgoing
8560 news and mail messages. The default is
8561 <var>syshostname</var>, your system's host name. Mail
8562 name ["<var>syshostname</var>"]:
8564 where <var>syshostname</var> is the output of <tt>hostname
8570 <heading>News system configuration</heading>
8573 All the configuration files related to the NNTP (news)
8574 servers and clients should be located under
8575 <file>/etc/news</file>.</p>
8578 There are some configuration issues that apply to a number
8579 of news clients and server packages on the machine. These
8583 <tag><file>/etc/news/organization</file></tag>
8585 A string which should appear as the
8586 organization header for all messages posted
8587 by NNTP clients on the machine
8590 <tag><file>/etc/news/server</file></tag>
8592 Contains the FQDN of the upstream NNTP
8593 server, or localhost if the local machine is
8598 Other global files may be added as required for cross-package news
8605 <heading>Programs for the X Window System</heading>
8608 <heading>Providing X support and package priorities</heading>
8611 Programs that can be configured with support for the X
8612 Window System must be configured to do so and must declare
8613 any package dependencies necessary to satisfy their
8614 runtime requirements when using the X Window System. If
8615 such a package is of higher priority than the X packages
8616 on which it depends, it is required that either the
8617 X-specific components be split into a separate package, or
8618 that an alternative version of the package, which includes
8619 X support, be provided, or that the package's priority be
8625 <heading>Packages providing an X server</heading>
8628 Packages that provide an X server that, directly or
8629 indirectly, communicates with real input and display
8630 hardware should declare in their <tt>Provides</tt> control
8631 field that they provide the virtual
8632 package <tt>xserver</tt>.<footnote>
8633 This implements current practice, and provides an
8634 actual policy for usage of the <tt>xserver</tt>
8635 virtual package which appears in the virtual packages
8636 list. In a nutshell, X servers that interface
8637 directly with the display and input hardware or via
8638 another subsystem (e.g., GGI) should provide
8639 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8640 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8646 <heading>Packages providing a terminal emulator</heading>
8649 Packages that provide a terminal emulator for the X Window
8650 System which meet the criteria listed below should declare in
8651 their <tt>Provides</tt> control field that they provide the
8652 virtual package <tt>x-terminal-emulator</tt>. They should
8653 also register themselves as an alternative for
8654 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8655 20. That alternative should have a slave alternative
8656 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8657 pointing to the corresponding manual page.
8661 To be an <tt>x-terminal-emulator</tt>, a program must:
8662 <list compact="compact">
8664 Be able to emulate a DEC VT100 terminal, or a
8665 compatible terminal.
8669 Support the command-line option <tt>-e
8670 <var>command</var></tt>, which creates a new
8671 terminal window<footnote>
8672 "New terminal window" does not necessarily mean
8673 a new top-level X window directly parented by
8674 the window manager; it could, if the terminal
8675 emulator application were so coded, be a new
8676 "view" in a multiple-document interface (MDI).
8678 and runs the specified <var>command</var>,
8679 interpreting the entirety of the rest of the command
8680 line as a command to pass straight to exec, in the
8681 manner that <tt>xterm</tt> does.
8685 Support the command-line option <tt>-T
8686 <var>title</var></tt>, which creates a new terminal
8687 window with the window title <var>title</var>.
8694 <heading>Packages providing a window manager</heading>
8697 Packages that provide a window manager should declare in
8698 their <tt>Provides</tt> control field that they provide the
8699 virtual package <tt>x-window-manager</tt>. They should also
8700 register themselves as an alternative for
8701 <file>/usr/bin/x-window-manager</file>, with a priority
8702 calculated as follows:
8703 <list compact="compact">
8705 Start with a priority of 20.
8709 If the window manager supports the Debian menu
8710 system, add 20 points if this support is available
8711 in the package's default configuration (i.e., no
8712 configuration files belonging to the system or user
8713 have to be edited to activate the feature); if
8714 configuration files must be modified, add only 10
8720 If the window manager complies with <url
8721 id="http://www.freedesktop.org/Standards/wm-spec"
8722 name="The Window Manager Specification Project">,
8723 written by the <url id="http://www.freedesktop.org/"
8724 name="Free Desktop Group">, add 40 points.
8728 If the window manager permits the X session to be
8729 restarted using a <em>different</em> window manager
8730 (without killing the X server) in its default
8731 configuration, add 10 points; otherwise add none.
8734 That alternative should have a slave alternative
8735 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8736 pointing to the corresponding manual page.
8741 <heading>Packages providing fonts</heading>
8744 Packages that provide fonts for the X Window
8746 For the purposes of Debian Policy, a "font for the X
8747 Window System" is one which is accessed via X protocol
8748 requests. Fonts for the Linux console, for PostScript
8749 renderer, or any other purpose, do not fit this
8750 definition. Any tool which makes such fonts available
8751 to the X Window System, however, must abide by this
8754 must do a number of things to ensure that they are both
8755 available without modification of the X or font server
8756 configuration, and that they do not corrupt files used by
8757 other font packages to register information about
8761 Fonts of any type supported by the X Window System
8762 must be in a separate binary package from any
8763 executables, libraries, or documentation (except
8764 that specific to the fonts shipped, such as their
8765 license information). If one or more of the fonts
8766 so packaged are necessary for proper operation of
8767 the package with which they are associated the font
8768 package may be Recommended; if the fonts merely
8769 provide an enhancement, a Suggests relationship may
8770 be used. Packages must not Depend on font
8772 This is because the X server may retrieve fonts
8773 from the local file system or over the network
8774 from an X font server; the Debian package system
8775 is empowered to deal only with the local
8781 BDF fonts must be converted to PCF fonts with the
8782 <prgn>bdftopcf</prgn> utility (available in the
8783 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8784 placed in a directory that corresponds to their
8786 <list compact="compact">
8788 100 dpi fonts must be placed in
8789 <file>/usr/share/fonts/X11/100dpi/</file>.
8793 75 dpi fonts must be placed in
8794 <file>/usr/share/fonts/X11/75dpi/</file>.
8798 Character-cell fonts, cursor fonts, and other
8799 low-resolution fonts must be placed in
8800 <file>/usr/share/fonts/X11/misc/</file>.
8806 Type 1 fonts must be placed in
8807 <file>/usr/share/fonts/X11/Type1/</file>. If font
8808 metric files are available, they must be placed here
8813 Subdirectories of <file>/usr/share/fonts/X11/</file>
8814 other than those listed above must be neither
8815 created nor used. (The <file>PEX</file>, <file>CID</file>,
8816 <file>Speedo</file>, and <file>cyrillic</file> directories
8817 are excepted for historical reasons, but installation of
8818 files into these directories remains discouraged.)
8822 Font packages may, instead of placing files directly
8823 in the X font directories listed above, provide
8824 symbolic links in that font directory pointing to
8825 the files' actual location in the filesystem. Such
8826 a location must comply with the FHS.
8830 Font packages should not contain both 75dpi and
8831 100dpi versions of a font. If both are available,
8832 they should be provided in separate binary packages
8833 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8834 the names of the packages containing the
8835 corresponding fonts.
8839 Fonts destined for the <file>misc</file> subdirectory
8840 should not be included in the same package as 75dpi
8841 or 100dpi fonts; instead, they should be provided in
8842 a separate package with <tt>-misc</tt> appended to
8847 Font packages must not provide the files
8848 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8849 <file>fonts.scale</file> in a font directory:
8852 <file>fonts.dir</file> files must not be provided at all.
8856 <file>fonts.alias</file> and <file>fonts.scale</file>
8857 files, if needed, should be provided in the
8859 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8860 where <var>fontdir</var> is the name of the
8862 <file>/usr/share/fonts/X11/</file> where the
8863 package's corresponding fonts are stored
8864 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8865 <var>package</var> is the name of the package
8866 that provides these fonts, and
8867 <var>extension</var> is either <tt>scale</tt>
8868 or <tt>alias</tt>, whichever corresponds to
8875 Font packages must declare a dependency on
8876 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
8877 or <tt>Pre-Depends</tt> control field.
8881 Font packages that provide one or more
8882 <file>fonts.scale</file> files as described above must
8883 invoke <prgn>update-fonts-scale</prgn> on each
8884 directory into which they installed fonts
8885 <em>before</em> invoking
8886 <prgn>update-fonts-dir</prgn> on that directory.
8887 This invocation must occur in both the
8888 <prgn>postinst</prgn> (for all arguments) and
8889 <prgn>postrm</prgn> (for all arguments except
8890 <tt>upgrade</tt>) scripts.
8894 Font packages that provide one or more
8895 <file>fonts.alias</file> files as described above must
8896 invoke <prgn>update-fonts-alias</prgn> on each
8897 directory into which they installed fonts. This
8898 invocation must occur in both the
8899 <prgn>postinst</prgn> (for all arguments) and
8900 <prgn>postrm</prgn> (for all arguments except
8901 <tt>upgrade</tt>) scripts.
8905 Font packages must invoke
8906 <prgn>update-fonts-dir</prgn> on each directory into
8907 which they installed fonts. This invocation must
8908 occur in both the <prgn>postinst</prgn> (for all
8909 arguments) and <prgn>postrm</prgn> (for all
8910 arguments except <tt>upgrade</tt>) scripts.
8914 Font packages must not provide alias names for the
8915 fonts they include which collide with alias names
8916 already in use by fonts already packaged.
8920 Font packages must not provide fonts with the same
8921 XLFD registry name as another font already packaged.
8927 <sect1 id="appdefaults">
8928 <heading>Application defaults files</heading>
8931 Application defaults files must be installed in the
8932 directory <file>/etc/X11/app-defaults/</file> (use of a
8933 localized subdirectory of <file>/etc/X11/</file> as described
8934 in the <em>X Toolkit Intrinsics - C Language
8935 Interface</em> manual is also permitted). They must be
8936 registered as <tt>conffile</tt>s or handled as
8937 configuration files.
8941 Customization of programs' X resources may also be
8942 supported with the provision of a file with the same name
8943 as that of the package placed in
8944 the <file>/etc/X11/Xresources/</file> directory, which
8945 must be registered as a <tt>conffile</tt> or handled as a
8946 configuration file.<footnote>
8947 Note that this mechanism is not the same as using
8948 app-defaults; app-defaults are tied to the client
8949 binary on the local file system, whereas X resources
8950 are stored in the X server and affect all connecting
8957 <heading>Installation directory issues</heading>
8960 Historically, packages using the X Window System used a
8961 separate set of installation directories from other packages.
8962 This practice has been discontinued and packages using the X
8963 Window System should now generally be installed in the same
8964 directories as any other package. Specifically, packages must
8965 not install files under the <file>/usr/X11R6/</file> directory
8966 and the <file>/usr/X11R6/</file> directory hierarchy should be
8967 regarded as obsolete.
8971 Include files previously installed under
8972 <file>/usr/X11R6/include/X11/</file> should be installed into
8973 <file>/usr/include/X11/</file>. For files previously
8974 installed into subdirectories of
8975 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8976 determine if subdirectories of <file>/usr/lib/</file> and
8977 <file>/usr/share/</file> can be used. If not, a subdirectory
8978 of <file>/usr/lib/X11/</file> should be used.
8982 Configuration files for window, display, or session managers
8983 or other applications that are tightly integrated with the X
8984 Window System may be placed in a subdirectory
8985 of <file>/etc/X11/</file> corresponding to the package name.
8986 Other X Window System applications should use
8987 the <file>/etc/</file> directory unless otherwise mandated by
8988 policy (such as for <ref id="appdefaults">).
8993 <heading>The OSF/Motif and OpenMotif libraries</heading>
8996 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8997 OpenMotif libraries</em><footnote>
8998 OSF/Motif and OpenMotif are collectively referred to as
8999 "Motif" in this policy document.
9001 should be compiled against and tested with LessTif (a free
9002 re-implementation of Motif) instead. If the maintainer
9003 judges that the program or programs do not work
9004 sufficiently well with LessTif to be distributed and
9005 supported, but do so when compiled against Motif, then two
9006 versions of the package should be created; one linked
9007 statically against Motif and with <tt>-smotif</tt>
9008 appended to the package name, and one linked dynamically
9009 against Motif and with <tt>-dmotif</tt> appended to the
9014 Both Motif-linked versions are dependent
9015 upon non-DFSG-compliant software and thus cannot be
9016 uploaded to the <em>main</em> distribution; if the
9017 software is itself DFSG-compliant it may be uploaded to
9018 the <em>contrib</em> distribution. While known existing
9019 versions of Motif permit unlimited redistribution of
9020 binaries linked against the library (whether statically or
9021 dynamically), it is the package maintainer's
9022 responsibility to determine whether this is permitted by
9023 the license of the copy of Motif in their possession.
9029 <heading>Perl programs and modules</heading>
9032 Perl programs and modules should follow the current Perl policy.
9036 The Perl policy can be found in the <tt>perl-policy</tt>
9037 files in the <tt>debian-policy</tt> package.
9038 It is also available from the Debian web mirrors at
9039 <tt><url name="/doc/packaging-manuals/perl-policy/"
9040 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9045 <heading>Emacs lisp programs</heading>
9048 Please refer to the "Debian Emacs Policy" for details of how to
9049 package emacs lisp programs.
9053 The Emacs policy is available in
9054 <file>debian-emacs-policy.gz</file> of the
9055 <package>emacsen-common</package> package.
9056 It is also available from the Debian web mirrors at
9057 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9058 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9063 <heading>Games</heading>
9066 The permissions on <file>/var/games</file> are mode 755, owner
9067 <tt>root</tt> and group <tt>root</tt>.
9071 Each game decides on its own security policy.</p>
9074 Games which require protected, privileged access to
9075 high-score files, saved games, etc., may be made
9076 set-<em>group</em>-id (mode 2755) and owned by
9077 <tt>root:games</tt>, and use files and directories with
9078 appropriate permissions (770 <tt>root:games</tt>, for
9079 example). They must not be made
9080 set-<em>user</em>-id, as this causes security problems. (If
9081 an attacker can subvert any set-user-id game they can
9082 overwrite the executable of any other, causing other players
9083 of these games to run a Trojan horse program. With a
9084 set-group-id game the attacker only gets access to less
9085 important game data, and if they can get at the other
9086 players' accounts at all it will take considerably more
9090 Some packages, for example some fortune cookie programs, are
9091 configured by the upstream authors to install with their
9092 data files or other static information made unreadable so
9093 that they can only be accessed through set-id programs
9094 provided. You should not do this in a Debian package: anyone can
9095 download the <file>.deb</file> file and read the data from it,
9096 so there is no point making the files unreadable. Not
9097 making the files unreadable also means that you don't have
9098 to make so many programs set-id, which reduces the risk of a
9102 As described in the FHS, binaries of games should be
9103 installed in the directory <file>/usr/games</file>. This also
9104 applies to games that use the X Window System. Manual pages
9105 for games (X and non-X games) should be installed in
9106 <file>/usr/share/man/man6</file>.</p>
9112 <heading>Documentation</heading>
9115 <heading>Manual pages</heading>
9118 You should install manual pages in <prgn>nroff</prgn> source
9119 form, in appropriate places under <file>/usr/share/man</file>.
9120 You should only use sections 1 to 9 (see the FHS for more
9121 details). You must not install a pre-formatted "cat page".
9125 Each program, utility, and function should have an
9126 associated manual page included in the same package. It is
9127 suggested that all configuration files also have a manual
9128 page included as well. Manual pages for protocols and other
9129 auxiliary things are optional.
9133 If no manual page is available, this is considered as a bug
9134 and should be reported to the Debian Bug Tracking System (the
9135 maintainer of the package is allowed to write this bug report
9136 themselves, if they so desire). Do not close the bug report
9137 until a proper man page is available.<footnote>
9138 It is not very hard to write a man page. See the
9139 <url id="http://www.schweikhardt.net/man_page_howto.html"
9140 name="Man-Page-HOWTO">,
9141 <manref name="man" section="7">, the examples
9142 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9143 the helper program <prgn>help2man</prgn>, or the
9144 directory <file>/usr/share/doc/man-db/examples</file>.
9149 You may forward a complaint about a missing man page to the
9150 upstream authors, and mark the bug as forwarded in the
9151 Debian bug tracking system. Even though the GNU Project do
9152 not in general consider the lack of a man page to be a bug,
9153 we do; if they tell you that they don't consider it a bug
9154 you should leave the bug in our bug tracking system open
9159 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9163 If one man page needs to be accessible via several names it
9164 is better to use a symbolic link than the <file>.so</file>
9165 feature, but there is no need to fiddle with the relevant
9166 parts of the upstream source to change from <file>.so</file> to
9167 symlinks: don't do it unless it's easy. You should not
9168 create hard links in the manual page directories, nor put
9169 absolute filenames in <file>.so</file> directives. The filename
9170 in a <file>.so</file> in a man page should be relative to the
9171 base of the man page tree (usually
9172 <file>/usr/share/man</file>). If you do not create any links
9173 (whether symlinks, hard links, or <tt>.so</tt> directives)
9174 in the file system to the alternate names of the man page,
9175 then you should not rely on <prgn>man</prgn> finding your
9176 man page under those names based solely on the information in
9177 the man page's header.<footnote>
9178 Supporting this in <prgn>man</prgn> often requires
9179 unreasonable processing time to find a manual page or to
9180 report that none exists, and moves knowledge into man's
9181 database that would be better left in the file system.
9182 This support is therefore deprecated and will cease to
9183 be present in the future.
9188 Manual pages in locale-specific subdirectories of
9189 <file>/usr/share/man</file> should use either UTF-8 or the usual
9190 legacy encoding for that language (normally the one corresponding
9191 to the shortest relevant locale name in
9192 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9193 <file>/usr/share/man/fr</file> should use either UTF-8 or
9194 ISO-8859-1.<footnote>
9195 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9196 use. In future, all manual pages will be required to use
9202 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9203 included in the subdirectory name unless it indicates a
9204 significant difference in the language, as this excludes
9205 speakers of the language in other countries.<footnote>
9206 At the time of writing, Chinese and Portuguese are the main
9207 languages with such differences, so <file>pt_BR</file>,
9208 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9213 If a localized version of a manual page is provided, it should
9214 either be up-to-date or it should be obvious to the reader that
9215 it is outdated and the original manual page should be used
9216 instead. This can be done either by a note at the beginning of
9217 the manual page or by showing the missing or changed portions in
9218 the original language instead of the target language.
9223 <heading>Info documents</heading>
9226 Info documents should be installed in <file>/usr/share/info</file>.
9227 They should be compressed with <tt>gzip -9</tt>.
9231 The <prgn>install-info</prgn> program maintains a directory of
9232 installed info documents in <file>/usr/share/info/dir</file> for
9233 the use of info readers.<footnote>
9234 It was previously necessary for packages installing info
9235 documents to run <prgn>install-info</prgn> from maintainer
9236 scripts. This is no longer necessary. The installation
9237 system now uses dpkg triggers.
9239 This file must not be included in packages. Packages containing
9240 info documents should depend on <tt>dpkg (>= 1.15.4) |
9241 install-info</tt> to ensure that the directory file is properly
9242 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9247 Info documents should contain section and directory entry
9248 information in the document for the use
9249 of <prgn>install-info</prgn>. The section should be specified
9250 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9251 space and the section of this info page. The directory entry or
9252 entries should be included between
9253 a <tt>START-INFO-DIR-ENTRY</tt> line and
9254 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9256 INFO-DIR-SECTION Individual utilities
9257 START-INFO-DIR-ENTRY
9258 * example: (example). An example info directory entry.
9261 To determine which section to use, you should look
9262 at <file>/usr/share/info/dir</file> on your system and choose
9263 the most relevant (or create a new section if none of the
9264 current sections are relevant).<footnote>
9265 Normally, info documents are generated from Texinfo source.
9266 To include this information in the generated info document, if
9267 it is absent, add commands like:
9269 @dircategory Individual utilities
9271 * example: (example). An example info directory entry.
9274 to the Texinfo source of the document and ensure that the info
9275 documents are rebuilt from source during the package build.
9281 <heading>Additional documentation</heading>
9284 Any additional documentation that comes with the package may
9285 be installed at the discretion of the package maintainer.
9286 Plain text documentation should be installed in the directory
9287 <file>/usr/share/doc/<var>package</var></file>, where
9288 <var>package</var> is the name of the package, and
9289 compressed with <tt>gzip -9</tt> unless it is small.
9293 If a package comes with large amounts of documentation which
9294 many users of the package will not require you should create
9295 a separate binary package to contain it, so that it does not
9296 take up disk space on the machines of users who do not need
9297 or want it installed.</p>
9300 It is often a good idea to put text information files
9301 (<file>README</file>s, changelogs, and so forth) that come with
9302 the source package in <file>/usr/share/doc/<var>package</var></file>
9303 in the binary package. However, you don't need to install
9304 the instructions for building and installing the package, of
9308 Packages must not require the existence of any files in
9309 <file>/usr/share/doc/</file> in order to function
9311 The system administrator should be able to
9312 delete files in <file>/usr/share/doc/</file> without causing
9313 any programs to break.
9315 Any files that are referenced by programs but are also
9316 useful as stand alone documentation should be installed under
9317 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9318 <file>/usr/share/doc/<var>package</var></file>.
9322 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9323 link to another directory in <file>/usr/share/doc</file> only if
9324 the two packages both come from the same source and the
9325 first package Depends on the second.<footnote>
9327 Please note that this does not override the section on
9328 changelog files below, so the file
9329 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9330 must refer to the changelog for the current version of
9331 <var>package</var> in question. In practice, this means
9332 that the sources of the target and the destination of the
9333 symlink must be the same (same source package and
9340 Former Debian releases placed all additional documentation
9341 in <file>/usr/doc/<var>package</var></file>. This has been
9342 changed to <file>/usr/share/doc/<var>package</var></file>,
9343 and packages must not put documentation in the directory
9344 <file>/usr/doc/<var>package</var></file>. <footnote>
9345 At this phase of the transition, we no longer require a
9346 symbolic link in <file>/usr/doc/</file>. At a later point,
9347 policy shall change to make the symbolic links a bug.
9353 <heading>Preferred documentation formats</heading>
9356 The unification of Debian documentation is being carried out
9360 If your package comes with extensive documentation in a
9361 markup format that can be converted to various other formats
9362 you should if possible ship HTML versions in a binary
9363 package, in the directory
9364 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9365 its subdirectories.<footnote>
9366 The rationale: The important thing here is that HTML
9367 docs should be available in <em>some</em> package, not
9368 necessarily in the main binary package.
9373 Other formats such as PostScript may be provided at the
9374 package maintainer's discretion.
9378 <sect id="copyrightfile">
9379 <heading>Copyright information</heading>
9382 Every package must be accompanied by a verbatim copy of its
9383 copyright information and distribution license in the file
9384 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9385 file must neither be compressed nor be a symbolic link.
9389 In addition, the copyright file must say where the upstream
9390 sources (if any) were obtained. It should name the original
9391 authors of the package and the Debian maintainer(s) who were
9392 involved with its creation.
9396 Packages in the <em>contrib</em> or <em>non-free</em> archive
9397 areas should state in the copyright file that the package is not
9398 part of the Debian GNU/Linux distribution and briefly explain
9403 A copy of the file which will be installed in
9404 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9405 be in <file>debian/copyright</file> in the source package.
9409 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9410 link to another directory in <file>/usr/share/doc</file> only if
9411 the two packages both come from the same source and the
9412 first package Depends on the second. These rules are
9413 important because copyrights must be extractable by
9418 Packages distributed under the Apache license (version 2.0), the
9419 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9420 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9421 1.3) should refer to the corresponding files
9422 under <file>/usr/share/common-licenses</file>,<footnote>
9425 <file>/usr/share/common-licenses/Apache-2.0</file>,
9426 <file>/usr/share/common-licenses/Artistic</file>,
9427 <file>/usr/share/common-licenses/GPL-1</file>,
9428 <file>/usr/share/common-licenses/GPL-2</file>,
9429 <file>/usr/share/common-licenses/GPL-3</file>,
9430 <file>/usr/share/common-licenses/LGPL-2</file>,
9431 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9432 <file>/usr/share/common-licenses/LGPL-3</file>,
9433 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9434 <file>/usr/share/common-licenses/GFDL-1.3</file>
9435 respectively. The University of California BSD license is
9436 also included in <package>base-files</package> as
9437 <file>/usr/share/common-licenses/BSD</file>, but given the
9438 brevity of this license, its specificity to code whose
9439 copyright is held by the Regents of the University of
9440 California, and the frequency of minor wording changes, its
9441 text should be included in the copyright file rather than
9442 referencing this file.
9444 </footnote> rather than quoting them in the copyright
9449 You should not use the copyright file as a general <file>README</file>
9450 file. If your package has such a file it should be
9451 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9452 <file>README.Debian</file> or some other appropriate place.</p>
9456 <heading>Examples</heading>
9459 Any examples (configurations, source files, whatever),
9460 should be installed in a directory
9461 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9462 files should not be referenced by any program: they're there
9463 for the benefit of the system administrator and users as
9464 documentation only. Architecture-specific example files
9465 should be installed in a directory
9466 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9468 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9469 latter directory itself may be a symbolic link to the
9474 If the purpose of a package is to provide examples, then the
9475 example files may be installed into
9476 <file>/usr/share/doc/<var>package</var></file>.
9480 <sect id="changelogs">
9481 <heading>Changelog files</heading>
9484 Packages that are not Debian-native must contain a
9485 compressed copy of the <file>debian/changelog</file> file from
9486 the Debian source tree in
9487 <file>/usr/share/doc/<var>package</var></file> with the name
9488 <file>changelog.Debian.gz</file>.
9492 If an upstream changelog is available, it should be accessible as
9493 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9494 plain text. If the upstream changelog is distributed in
9495 HTML, it should be made available in that form as
9496 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9497 and a plain text <file>changelog.gz</file> should be generated
9498 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9499 the upstream changelog files do not already conform to this
9500 naming convention, then this may be achieved either by
9501 renaming the files, or by adding a symbolic link, at the
9502 maintainer's discretion.<footnote>
9503 Rationale: People should not have to look in places for
9504 upstream changelogs merely because they are given
9505 different names or are distributed in HTML format.
9510 All of these files should be installed compressed using
9511 <tt>gzip -9</tt>, as they will become large with time even
9512 if they start out small.
9516 If the package has only one changelog which is used both as
9517 the Debian changelog and the upstream one because there is
9518 no separate upstream maintainer then that changelog should
9519 usually be installed as
9520 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9521 there is a separate upstream maintainer, but no upstream
9522 changelog, then the Debian changelog should still be called
9523 <file>changelog.Debian.gz</file>.
9527 For details about the format and contents of the Debian
9528 changelog file, please see <ref id="dpkgchangelog">.
9533 <appendix id="pkg-scope">
9534 <heading>Introduction and scope of these appendices</heading>
9537 These appendices are taken essentially verbatim from the
9538 now-deprecated Packaging Manual, version 3.2.1.0. They are
9539 the chapters which are likely to be of use to package
9540 maintainers and which have not already been included in the
9541 policy document itself. Most of these sections are very likely
9542 not relevant to policy; they should be treated as
9543 documentation for the packaging system. Please note that these
9544 appendices are included for convenience, and for historical
9545 reasons: they used to be part of policy package, and they have
9546 not yet been incorporated into dpkg documentation. However,
9547 they still have value, and hence they are presented here.
9551 They have not yet been checked to ensure that they are
9552 compatible with the contents of policy, and if there are any
9553 contradictions, the version in the main policy document takes
9554 precedence. The remaining chapters of the old Packaging
9555 Manual have also not been read in detail to ensure that there
9556 are not parts which have been left out. Both of these will be
9561 Certain parts of the Packaging manual were integrated into the
9562 Policy Manual proper, and removed from the appendices. Links
9563 have been placed from the old locations to the new ones.
9567 <prgn>dpkg</prgn> is a suite of programs for creating binary
9568 package files and installing and removing them on Unix
9570 <prgn>dpkg</prgn> is targeted primarily at Debian
9571 GNU/Linux, but may work on or be ported to other
9577 The binary packages are designed for the management of
9578 installed executable programs (usually compiled binaries) and
9579 their associated data, though source code examples and
9580 documentation are provided as part of some packages.</p>
9583 This manual describes the technical aspects of creating Debian
9584 binary packages (<file>.deb</file> files). It documents the
9585 behavior of the package management programs
9586 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9587 they interact with packages.</p>
9590 It also documents the interaction between
9591 <prgn>dselect</prgn>'s core and the access method scripts it
9592 uses to actually install the selected packages, and describes
9593 how to create a new access method.</p>
9596 This manual does not go into detail about the options and
9597 usage of the package building and installation tools. It
9598 should therefore be read in conjunction with those programs'
9603 The utility programs which are provided with <prgn>dpkg</prgn>
9604 for managing various system configuration and similar issues,
9605 such as <prgn>update-rc.d</prgn> and
9606 <prgn>install-info</prgn>, are not described in detail here -
9607 please see their man pages.
9611 It is assumed that the reader is reasonably familiar with the
9612 <prgn>dpkg</prgn> System Administrators' manual.
9613 Unfortunately this manual does not yet exist.
9617 The Debian version of the FSF's GNU hello program is provided
9618 as an example for people wishing to create Debian
9619 packages. The Debian <prgn>debmake</prgn> package is
9620 recommended as a very helpful tool in creating and maintaining
9621 Debian packages. However, while the tools and examples are
9622 helpful, they do not replace the need to read and follow the
9623 Policy and Programmer's Manual.</p>
9626 <appendix id="pkg-binarypkg">
9627 <heading>Binary packages (from old Packaging Manual)</heading>
9630 The binary package has two main sections. The first part
9631 consists of various control information files and scripts used
9632 by <prgn>dpkg</prgn> when installing and removing. See <ref
9633 id="pkg-controlarea">.
9637 The second part is an archive containing the files and
9638 directories to be installed.
9642 In the future binary packages may also contain other
9643 components, such as checksums and digital signatures. The
9644 format for the archive is described in full in the
9645 <file>deb(5)</file> man page.
9649 <sect id="pkg-bincreating"><heading>Creating package files -
9650 <prgn>dpkg-deb</prgn>
9654 All manipulation of binary package files is done by
9655 <prgn>dpkg-deb</prgn>; it's the only program that has
9656 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9657 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9658 will spot that the options requested are appropriate to
9659 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9664 In order to create a binary package you must make a
9665 directory tree which contains all the files and directories
9666 you want to have in the file system data part of the package.
9667 In Debian-format source packages this directory is usually
9668 <file>debian/tmp</file>, relative to the top of the package's
9673 They should have the locations (relative to the root of the
9674 directory tree you're constructing) ownerships and
9675 permissions which you want them to have on the system when
9680 With current versions of <prgn>dpkg</prgn> the uid/username
9681 and gid/groupname mappings for the users and groups being
9682 used should be the same on the system where the package is
9683 built and the one where it is installed.
9687 You need to add one special directory to the root of the
9688 miniature file system tree you're creating:
9689 <prgn>DEBIAN</prgn>. It should contain the control
9690 information files, notably the binary package control file
9691 (see <ref id="pkg-controlfile">).
9695 The <prgn>DEBIAN</prgn> directory will not appear in the
9696 file system archive of the package, and so won't be installed
9697 by <prgn>dpkg</prgn> when the package is installed.
9701 When you've prepared the package, you should invoke:
9703 dpkg --build <var>directory</var>
9708 This will build the package in
9709 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9710 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9711 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9716 See the man page <manref name="dpkg-deb" section="8"> for details of how
9717 to examine the contents of this newly-created file. You may find the
9718 output of following commands enlightening:
9720 dpkg-deb --info <var>filename</var>.deb
9721 dpkg-deb --contents <var>filename</var>.deb
9722 dpkg --contents <var>filename</var>.deb
9724 To view the copyright file for a package you could use this command:
9726 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9731 <sect id="pkg-controlarea">
9732 <heading>Package control information files</heading>
9735 The control information portion of a binary package is a
9736 collection of files with names known to <prgn>dpkg</prgn>.
9737 It will treat the contents of these files specially - some
9738 of them contain information used by <prgn>dpkg</prgn> when
9739 installing or removing the package; others are scripts which
9740 the package maintainer wants <prgn>dpkg</prgn> to run.
9744 It is possible to put other files in the package control
9745 information file area, but this is not generally a good idea
9746 (though they will largely be ignored).
9750 Here is a brief list of the control information files supported
9751 by <prgn>dpkg</prgn> and a summary of what they're used for.
9756 <tag><tt>control</tt>
9759 This is the key description file used by
9760 <prgn>dpkg</prgn>. It specifies the package's name
9761 and version, gives its description for the user,
9762 states its relationships with other packages, and so
9763 forth. See <ref id="sourcecontrolfiles"> and
9764 <ref id="binarycontrolfiles">.
9768 It is usually generated automatically from information
9769 in the source package by the
9770 <prgn>dpkg-gencontrol</prgn> program, and with
9771 assistance from <prgn>dpkg-shlibdeps</prgn>.
9772 See <ref id="pkg-sourcetools">.
9776 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9781 These are executable files (usually scripts) which
9782 <prgn>dpkg</prgn> runs during installation, upgrade
9783 and removal of packages. They allow the package to
9784 deal with matters which are particular to that package
9785 or require more complicated processing than that
9786 provided by <prgn>dpkg</prgn>. Details of when and
9787 how they are called are in <ref id="maintainerscripts">.
9791 It is very important to make these scripts idempotent.
9792 See <ref id="idempotency">.
9796 The maintainer scripts are not guaranteed to run with a
9797 controlling terminal and may not be able to interact with
9798 the user. See <ref id="controllingterminal">.
9802 <tag><tt>conffiles</tt>
9805 This file contains a list of configuration files which
9806 are to be handled automatically by <prgn>dpkg</prgn>
9807 (see <ref id="pkg-conffiles">). Note that not necessarily
9808 every configuration file should be listed here.
9811 <tag><tt>shlibs</tt>
9814 This file contains a list of the shared libraries
9815 supplied by the package, with dependency details for
9816 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9817 when it determines what dependencies are required in a
9818 package control file. The <tt>shlibs</tt> file format
9819 is described on <ref id="shlibs">.
9824 <sect id="pkg-controlfile">
9825 <heading>The main control information file: <tt>control</tt></heading>
9828 The most important control information file used by
9829 <prgn>dpkg</prgn> when it installs a package is
9830 <tt>control</tt>. It contains all the package's "vital
9835 The binary package control files of packages built from
9836 Debian sources are made by a special tool,
9837 <prgn>dpkg-gencontrol</prgn>, which reads
9838 <file>debian/control</file> and <file>debian/changelog</file> to
9839 find the information it needs. See <ref id="pkg-sourcepkg"> for
9844 The fields in binary package control files are listed in
9845 <ref id="binarycontrolfiles">.
9849 A description of the syntax of control files and the purpose
9850 of the fields is available in <ref id="controlfields">.
9855 <heading>Time Stamps</heading>
9858 See <ref id="timestamps">.
9863 <appendix id="pkg-sourcepkg">
9864 <heading>Source packages (from old Packaging Manual) </heading>
9867 The Debian binary packages in the distribution are generated
9868 from Debian sources, which are in a special format to assist
9869 the easy and automatic building of binaries.
9872 <sect id="pkg-sourcetools">
9873 <heading>Tools for processing source packages</heading>
9876 Various tools are provided for manipulating source packages;
9877 they pack and unpack sources and help build of binary
9878 packages and help manage the distribution of new versions.
9882 They are introduced and typical uses described here; see
9883 <manref name="dpkg-source" section="1"> for full
9884 documentation about their arguments and operation.
9888 For examples of how to construct a Debian source package,
9889 and how to use those utilities that are used by Debian
9890 source packages, please see the <prgn>hello</prgn> example
9894 <sect1 id="pkg-dpkg-source">
9896 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9901 This program is frequently used by hand, and is also
9902 called from package-independent automated building scripts
9903 such as <prgn>dpkg-buildpackage</prgn>.
9907 To unpack a package it is typically invoked with
9909 dpkg-source -x <var>.../path/to/filename</var>.dsc
9914 with the <file><var>filename</var>.tar.gz</file> and
9915 <file><var>filename</var>.diff.gz</file> (if applicable) in
9916 the same directory. It unpacks into
9917 <file><var>package</var>-<var>version</var></file>, and if
9919 <file><var>package</var>-<var>version</var>.orig</file>, in
9920 the current directory.
9924 To create a packed source archive it is typically invoked:
9926 dpkg-source -b <var>package</var>-<var>version</var>
9931 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9932 <file>.diff.gz</file> (if appropriate) in the current
9933 directory. <prgn>dpkg-source</prgn> does not clean the
9934 source tree first - this must be done separately if it is
9939 See also <ref id="pkg-sourcearchives">.</p>
9943 <sect1 id="pkg-dpkg-buildpackage">
9945 <prgn>dpkg-buildpackage</prgn> - overall package-building
9950 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9951 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9952 targets <tt>clean</tt>, <tt>build</tt> and
9953 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9954 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9955 source and binary package upload.
9959 It is usually invoked by hand from the top level of the
9960 built or unbuilt source directory. It may be invoked with
9961 no arguments; useful arguments include:
9962 <taglist compact="compact">
9963 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9966 Do not sign the <tt>.changes</tt> file or the
9967 source package <tt>.dsc</tt> file, respectively.</p>
9969 <tag><tt>-p<var>sign-command</var></tt></tag>
9972 Invoke <var>sign-command</var> instead of finding
9973 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9974 <var>sign-command</var> must behave just like
9975 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9977 <tag><tt>-r<var>root-command</var></tt></tag>
9980 When root privilege is required, invoke the command
9981 <var>root-command</var>. <var>root-command</var>
9982 should invoke its first argument as a command, from
9983 the <prgn>PATH</prgn> if necessary, and pass its
9984 second and subsequent arguments to the command it
9985 calls. If no <var>root-command</var> is supplied
9986 then <var>dpkg-buildpackage</var> will take no
9987 special action to gain root privilege, so that for
9988 most packages it will have to be invoked as root to
9991 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9994 Two types of binary-only build and upload - see
9995 <manref name="dpkg-source" section="1">.
10002 <sect1 id="pkg-dpkg-gencontrol">
10004 <prgn>dpkg-gencontrol</prgn> - generates binary package
10009 This program is usually called from <file>debian/rules</file>
10010 (see <ref id="pkg-sourcetree">) in the top level of the source
10015 This is usually done just before the files and directories in the
10016 temporary directory tree where the package is being built have their
10017 permissions and ownerships set and the package is constructed using
10018 <prgn>dpkg-deb/</prgn>
10020 This is so that the control file which is produced has
10021 the right permissions
10026 <prgn>dpkg-gencontrol</prgn> must be called after all the
10027 files which are to go into the package have been placed in
10028 the temporary build directory, so that its calculation of
10029 the installed size of a package is correct.
10033 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10034 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10035 variable substitutions created by
10036 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10041 For a package which generates only one binary package, and
10042 which builds it in <file>debian/tmp</file> relative to the top
10043 of the source package, it is usually sufficient to call
10044 <prgn>dpkg-gencontrol</prgn>.
10048 Sources which build several binaries will typically need
10051 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10052 </example> The <tt>-P</tt> tells
10053 <prgn>dpkg-gencontrol</prgn> that the package is being
10054 built in a non-default directory, and the <tt>-p</tt>
10055 tells it which package's control file should be generated.
10059 <prgn>dpkg-gencontrol</prgn> also adds information to the
10060 list of files in <file>debian/files</file>, for the benefit of
10061 (for example) a future invocation of
10062 <prgn>dpkg-genchanges</prgn>.</p>
10065 <sect1 id="pkg-dpkg-shlibdeps">
10067 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10072 This program is usually called from <file>debian/rules</file>
10073 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10074 id="pkg-sourcetree">), in the top level of the source tree.
10078 Its arguments are executables and shared libraries
10081 They may be specified either in the locations in the
10082 source tree where they are created or in the locations
10083 in the temporary build tree where they are installed
10084 prior to binary package creation.
10086 </footnote> for which shared library dependencies should
10087 be included in the binary package's control file.
10091 If some of the found shared libraries should only
10092 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10093 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10094 by using the <tt>-d<var>dependency-field</var></tt> option
10095 before those executable(s). (Each <tt>-d</tt> option
10096 takes effect until the next <tt>-d</tt>.)
10100 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10101 output control file to be modified. Instead by default it
10102 adds to the <file>debian/substvars</file> file variable
10103 settings like <tt>shlibs:Depends</tt>. These variable
10104 settings must be referenced in dependency fields in the
10105 appropriate per-binary-package sections of the source
10110 For example, a package that generates an essential part
10111 which requires dependencies, and optional parts that
10112 which only require a recommendation, would separate those
10113 two sets of dependencies into two different fields.<footnote>
10114 At the time of writing, an example for this was the
10115 <package/xmms/ package, with Depends used for the xmms
10116 executable, Recommends for the plug-ins and Suggests for
10117 even more optional features provided by unzip.
10119 It can say in its <file>debian/rules</file>:
10121 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10122 -dRecommends <var>optionalpart anotheroptionalpart</var>
10124 and then in its main control file <file>debian/control</file>:
10127 Depends: ${shlibs:Depends}
10128 Recommends: ${shlibs:Recommends}
10134 Sources which produce several binary packages with
10135 different shared library dependency requirements can use
10136 the <tt>-p<var>varnameprefix</var></tt> option to override
10137 the default <tt>shlibs:</tt> prefix (one invocation of
10138 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10139 They can thus produce several sets of dependency
10140 variables, each of the form
10141 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10142 which can be referred to in the appropriate parts of the
10143 binary package control files.
10148 <sect1 id="pkg-dpkg-distaddfile">
10150 <prgn>dpkg-distaddfile</prgn> - adds a file to
10151 <file>debian/files</file>
10155 Some packages' uploads need to include files other than
10156 the source and binary package files.
10160 <prgn>dpkg-distaddfile</prgn> adds a file to the
10161 <file>debian/files</file> file so that it will be included in
10162 the <file>.changes</file> file when
10163 <prgn>dpkg-genchanges</prgn> is run.
10167 It is usually invoked from the <tt>binary</tt> target of
10168 <file>debian/rules</file>:
10170 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10172 The <var>filename</var> is relative to the directory where
10173 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10174 is usually the directory above the top level of the source
10175 tree. The <file>debian/rules</file> target should put the
10176 file there just before or just after calling
10177 <prgn>dpkg-distaddfile</prgn>.
10181 The <var>section</var> and <var>priority</var> are passed
10182 unchanged into the resulting <file>.changes</file> file.
10187 <sect1 id="pkg-dpkg-genchanges">
10189 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10190 upload control file
10194 This program is usually called by package-independent
10195 automatic building scripts such as
10196 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10201 It is usually called in the top level of a built source
10202 tree, and when invoked with no arguments will print out a
10203 straightforward <file>.changes</file> file based on the
10204 information in the source package's changelog and control
10205 file and the binary and source packages which should have
10211 <sect1 id="pkg-dpkg-parsechangelog">
10213 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10214 representation of a changelog
10218 This program is used internally by
10219 <prgn>dpkg-source</prgn> et al. It may also occasionally
10220 be useful in <file>debian/rules</file> and elsewhere. It
10221 parses a changelog, <file>debian/changelog</file> by default,
10222 and prints a control-file format representation of the
10223 information in it to standard output.
10227 <sect1 id="pkg-dpkg-architecture">
10229 <prgn>dpkg-architecture</prgn> - information about the build and
10234 This program can be used manually, but is also invoked by
10235 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10236 environment or make variables which specify the build and host
10237 architecture for the package building process.
10242 <sect id="pkg-sourcetree">
10243 <heading>The Debian package source tree</heading>
10246 The source archive scheme described later is intended to
10247 allow a Debian package source tree with some associated
10248 control information to be reproduced and transported easily.
10249 The Debian package source tree is a version of the original
10250 program with certain files added for the benefit of the
10251 packaging process, and with any other changes required
10252 made to the rest of the source code and installation
10257 The extra files created for Debian are in the subdirectory
10258 <file>debian</file> of the top level of the Debian package
10259 source tree. They are described below.
10262 <sect1 id="pkg-debianrules">
10263 <heading><file>debian/rules</file> - the main building script</heading>
10266 See <ref id="debianrules">.
10270 <sect1 id="pkg-srcsubstvars">
10271 <heading><file>debian/substvars</file> and variable substitutions</heading>
10274 See <ref id="substvars">.
10280 <heading><file>debian/files</file></heading>
10283 See <ref id="debianfiles">.
10287 <sect1><heading><file>debian/tmp</file>
10291 This is the canonical temporary location for the
10292 construction of binary packages by the <tt>binary</tt>
10293 target. The directory <file>tmp</file> serves as the root of
10294 the file system tree as it is being constructed (for
10295 example, by using the package's upstream makefiles install
10296 targets and redirecting the output there), and it also
10297 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10298 id="pkg-bincreating">.
10302 If several binary packages are generated from the same
10303 source tree it is usual to use several
10304 <file>debian/tmp<var>something</var></file> directories, for
10305 example <file>tmp-a</file> or <file>tmp-doc</file>.
10309 Whatever <file>tmp</file> directories are created and used by
10310 <tt>binary</tt> must of course be removed by the
10311 <tt>clean</tt> target.</p></sect1>
10315 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10319 As it exists on the FTP site, a Debian source package
10320 consists of three related files. You must have the right
10321 versions of all three to be able to use them.
10326 <tag>Debian source control file - <tt>.dsc</tt></tag>
10328 This file is a control file used by <prgn>dpkg-source</prgn>
10329 to extract a source package.
10330 See <ref id="debiansourcecontrolfiles">.
10334 Original source archive -
10336 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10342 This is a compressed (with <tt>gzip -9</tt>)
10343 <prgn>tar</prgn> file containing the source code from
10344 the upstream authors of the program.
10349 Debian package diff -
10351 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10357 This is a unified context diff (<tt>diff -u</tt>)
10358 giving the changes which are required to turn the
10359 original source into the Debian source. These changes
10360 may only include editing and creating plain files.
10361 The permissions of files, the targets of symbolic
10362 links and the characteristics of special files or
10363 pipes may not be changed and no files may be removed
10368 All the directories in the diff must exist, except the
10369 <file>debian</file> subdirectory of the top of the source
10370 tree, which will be created by
10371 <prgn>dpkg-source</prgn> if necessary when unpacking.
10375 The <prgn>dpkg-source</prgn> program will
10376 automatically make the <file>debian/rules</file> file
10377 executable (see below).</p></item>
10382 If there is no original source code - for example, if the
10383 package is specially prepared for Debian or the Debian
10384 maintainer is the same as the upstream maintainer - the
10385 format is slightly different: then there is no diff, and the
10387 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10388 and preferably contains a directory named
10389 <file><var>package</var>-<var>version</var></file>.
10394 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10397 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10398 Debian source package. However, if it is not available it
10399 is possible to unpack a Debian source archive as follows:
10400 <enumlist compact="compact">
10403 Untar the tarfile, which will create a <file>.orig</file>
10407 <p>Rename the <file>.orig</file> directory to
10408 <file><var>package</var>-<var>version</var></file>.</p>
10412 Create the subdirectory <file>debian</file> at the top of
10413 the source tree.</p>
10415 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10417 <item><p>Untar the tarfile again if you want a copy of the original
10418 source code alongside the Debian version.</p>
10423 It is not possible to generate a valid Debian source archive
10424 without using <prgn>dpkg-source</prgn>. In particular,
10425 attempting to use <prgn>diff</prgn> directly to generate the
10426 <file>.diff.gz</file> file will not work.
10430 <heading>Restrictions on objects in source packages</heading>
10433 The source package may not contain any hard links
10435 This is not currently detected when building source
10436 packages, but only when extracting
10440 Hard links may be permitted at some point in the
10441 future, but would require a fair amount of
10443 </footnote>, device special files, sockets or setuid or
10446 Setgid directories are allowed.
10451 The source packaging tools manage the changes between the
10452 original and Debian source using <prgn>diff</prgn> and
10453 <prgn>patch</prgn>. Turning the original source tree as
10454 included in the <file>.orig.tar.gz</file> into the Debian
10455 package source must not involve any changes which cannot be
10456 handled by these tools. Problematic changes which cause
10457 <prgn>dpkg-source</prgn> to halt with an error when
10458 building the source package are:
10459 <list compact="compact">
10460 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10462 <item><p>Changing the targets of symbolic links.</p>
10464 <item><p>Creating directories, other than <file>debian</file>.</p>
10466 <item><p>Changes to the contents of binary files.</p></item>
10467 </list> Changes which cause <prgn>dpkg-source</prgn> to
10468 print a warning but continue anyway are:
10469 <list compact="compact">
10472 Removing files, directories or symlinks.
10474 Renaming a file is not treated specially - it is
10475 seen as the removal of the old file (which
10476 generates a warning, but is otherwise ignored),
10477 and the creation of the new one.
10483 Changed text files which are missing the usual final
10484 newline (either in the original or the modified
10489 Changes which are not represented, but which are not detected by
10490 <prgn>dpkg-source</prgn>, are:
10491 <list compact="compact">
10492 <item><p>Changing the permissions of files (other than
10493 <file>debian/rules</file>) and directories.</p></item>
10498 The <file>debian</file> directory and <file>debian/rules</file>
10499 are handled specially by <prgn>dpkg-source</prgn> - before
10500 applying the changes it will create the <file>debian</file>
10501 directory, and afterwards it will make
10502 <file>debian/rules</file> world-executable.
10508 <appendix id="pkg-controlfields">
10509 <heading>Control files and their fields (from old Packaging Manual)</heading>
10512 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10513 data in a common format, known as control files. Binary and
10514 source packages have control data as do the <file>.changes</file>
10515 files which control the installation of uploaded files, and
10516 <prgn>dpkg</prgn>'s internal databases are in a similar
10521 <heading>Syntax of control files</heading>
10524 See <ref id="controlsyntax">.
10528 It is important to note that there are several fields which
10529 are optional as far as <prgn>dpkg</prgn> and the related
10530 tools are concerned, but which must appear in every Debian
10531 package, or whose omission may cause problems.
10536 <heading>List of fields</heading>
10539 See <ref id="controlfieldslist">.
10543 This section now contains only the fields that didn't belong
10544 to the Policy manual.
10547 <sect1 id="pkg-f-Filename">
10548 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10551 These fields in <tt>Packages</tt> files give the
10552 filename(s) of (the parts of) a package in the
10553 distribution directories, relative to the root of the
10554 Debian hierarchy. If the package has been split into
10555 several parts the parts are all listed in order, separated
10560 <sect1 id="pkg-f-Size">
10561 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10564 These fields in <file>Packages</file> files give the size (in
10565 bytes, expressed in decimal) and MD5 checksum of the
10566 file(s) which make(s) up a binary package in the
10567 distribution. If the package is split into several parts
10568 the values for the parts are listed in order, separated by
10573 <sect1 id="pkg-f-Status">
10574 <heading><tt>Status</tt></heading>
10577 This field in <prgn>dpkg</prgn>'s status file records
10578 whether the user wants a package installed, removed or
10579 left alone, whether it is broken (requiring
10580 re-installation) or not and what its current state on the
10581 system is. Each of these pieces of information is a
10586 <sect1 id="pkg-f-Config-Version">
10587 <heading><tt>Config-Version</tt></heading>
10590 If a package is not installed or not configured, this
10591 field in <prgn>dpkg</prgn>'s status file records the last
10592 version of the package which was successfully
10597 <sect1 id="pkg-f-Conffiles">
10598 <heading><tt>Conffiles</tt></heading>
10601 This field in <prgn>dpkg</prgn>'s status file contains
10602 information about the automatically-managed configuration
10603 files held by a package. This field should <em>not</em>
10604 appear anywhere in a package!
10609 <heading>Obsolete fields</heading>
10612 These are still recognized by <prgn>dpkg</prgn> but should
10613 not appear anywhere any more.
10615 <taglist compact="compact">
10617 <tag><tt>Revision</tt></tag>
10618 <tag><tt>Package-Revision</tt></tag>
10619 <tag><tt>Package_Revision</tt></tag>
10621 The Debian revision part of the package version was
10622 at one point in a separate control field. This
10623 field went through several names.
10626 <tag><tt>Recommended</tt></tag>
10627 <item>Old name for <tt>Recommends</tt>.</item>
10629 <tag><tt>Optional</tt></tag>
10630 <item>Old name for <tt>Suggests</tt>.</item>
10632 <tag><tt>Class</tt></tag>
10633 <item>Old name for <tt>Priority</tt>.</item>
10642 <appendix id="pkg-conffiles">
10643 <heading>Configuration file handling (from old Packaging Manual)</heading>
10646 <prgn>dpkg</prgn> can do a certain amount of automatic
10647 handling of package configuration files.
10651 Whether this mechanism is appropriate depends on a number of
10652 factors, but basically there are two approaches to any
10653 particular configuration file.
10657 The easy method is to ship a best-effort configuration in the
10658 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10659 handle updates. If the user is unlikely to want to edit the
10660 file, but you need them to be able to without losing their
10661 changes, and a new package with a changed version of the file
10662 is only released infrequently, this is a good approach.
10666 The hard method is to build the configuration file from
10667 scratch in the <prgn>postinst</prgn> script, and to take the
10668 responsibility for fixing any mistakes made in earlier
10669 versions of the package automatically. This will be
10670 appropriate if the file is likely to need to be different on
10674 <sect><heading>Automatic handling of configuration files by
10679 A package may contain a control information file called
10680 <tt>conffiles</tt>. This file should be a list of filenames
10681 of configuration files needing automatic handling, separated
10682 by newlines. The filenames should be absolute pathnames,
10683 and the files referred to should actually exist in the
10688 When a package is upgraded <prgn>dpkg</prgn> will process
10689 the configuration files during the configuration stage,
10690 shortly before it runs the package's <prgn>postinst</prgn>
10695 For each file it checks to see whether the version of the
10696 file included in the package is the same as the one that was
10697 included in the last version of the package (the one that is
10698 being upgraded from); it also compares the version currently
10699 installed on the system with the one shipped with the last
10704 If neither the user nor the package maintainer has changed
10705 the file, it is left alone. If one or the other has changed
10706 their version, then the changed version is preferred - i.e.,
10707 if the user edits their file, but the package maintainer
10708 doesn't ship a different version, the user's changes will
10709 stay, silently, but if the maintainer ships a new version
10710 and the user hasn't edited it the new version will be
10711 installed (with an informative message). If both have
10712 changed their version the user is prompted about the problem
10713 and must resolve the differences themselves.
10717 The comparisons are done by calculating the MD5 message
10718 digests of the files, and storing the MD5 of the file as it
10719 was included in the most recent version of the package.
10723 When a package is installed for the first time
10724 <prgn>dpkg</prgn> will install the file that comes with it,
10725 unless that would mean overwriting a file already on the
10730 However, note that <prgn>dpkg</prgn> will <em>not</em>
10731 replace a conffile that was removed by the user (or by a
10732 script). This is necessary because with some programs a
10733 missing file produces an effect hard or impossible to
10734 achieve in another way, so that a missing file needs to be
10735 kept that way if the user did it.
10739 Note that a package should <em>not</em> modify a
10740 <prgn>dpkg</prgn>-handled conffile in its maintainer
10741 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10742 the user confusing and possibly dangerous options for
10743 conffile update when the package is upgraded.</p>
10746 <sect><heading>Fully-featured maintainer script configuration
10751 For files which contain site-specific information such as
10752 the hostname and networking details and so forth, it is
10753 better to create the file in the package's
10754 <prgn>postinst</prgn> script.
10758 This will typically involve examining the state of the rest
10759 of the system to determine values and other information, and
10760 may involve prompting the user for some information which
10761 can't be obtained some other way.
10765 When using this method there are a couple of important
10766 issues which should be considered:
10770 If you discover a bug in the program which generates the
10771 configuration file, or if the format of the file changes
10772 from one version to the next, you will have to arrange for
10773 the postinst script to do something sensible - usually this
10774 will mean editing the installed configuration file to remove
10775 the problem or change the syntax. You will have to do this
10776 very carefully, since the user may have changed the file,
10777 perhaps to fix the very problem that your script is trying
10778 to deal with - you will have to detect these situations and
10779 deal with them correctly.
10783 If you do go down this route it's probably a good idea to
10784 make the program that generates the configuration file(s) a
10785 separate program in <file>/usr/sbin</file>, by convention called
10786 <file><var>package</var>config</file> and then run that if
10787 appropriate from the post-installation script. The
10788 <tt><var>package</var>config</tt> program should not
10789 unquestioningly overwrite an existing configuration - if its
10790 mode of operation is geared towards setting up a package for
10791 the first time (rather than any arbitrary reconfiguration
10792 later) you should have it check whether the configuration
10793 already exists, and require a <tt>--force</tt> flag to
10794 overwrite it.</p></sect>
10797 <appendix id="pkg-alternatives"><heading>Alternative versions of
10798 an interface - <prgn>update-alternatives</prgn> (from old
10803 When several packages all provide different versions of the
10804 same program or file it is useful to have the system select a
10805 default, but to allow the system administrator to change it
10806 and have their decisions respected.
10810 For example, there are several versions of the <prgn>vi</prgn>
10811 editor, and there is no reason to prevent all of them from
10812 being installed at once, each under their own name
10813 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10814 Nevertheless it is desirable to have the name <tt>vi</tt>
10815 refer to something, at least by default.
10819 If all the packages involved cooperate, this can be done with
10820 <prgn>update-alternatives</prgn>.
10824 Each package provides its own version under its own name, and
10825 calls <prgn>update-alternatives</prgn> in its postinst to
10826 register its version (and again in its prerm to deregister
10831 See the man page <manref name="update-alternatives"
10832 section="8"> for details.
10836 If <prgn>update-alternatives</prgn> does not seem appropriate
10837 you may wish to consider using diversions instead.</p>
10840 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10841 package's version of a file (from old Packaging Manual)
10845 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10846 when it reinstalls the package it belongs to, and to have it
10847 put the file from the package somewhere else instead.
10851 This can be used locally to override a package's version of a
10852 file, or by one package to override another's version (or
10853 provide a wrapper for it).
10857 Before deciding to use a diversion, read <ref
10858 id="pkg-alternatives"> to see if you really want a diversion
10859 rather than several alternative versions of a program.
10863 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10864 and updated by a special program <prgn>dpkg-divert</prgn>.
10865 Please see <manref name="dpkg-divert" section="8"> for full
10866 details of its operation.
10870 When a package wishes to divert a file from another, it should
10871 call <prgn>dpkg-divert</prgn> in its preinst to add the
10872 diversion and rename the existing file. For example,
10873 supposing that a <prgn>smailwrapper</prgn> package wishes to
10874 install a wrapper around <file>/usr/sbin/smail</file>:
10876 dpkg-divert --package smailwrapper --add --rename \
10877 --divert /usr/sbin/smail.real /usr/sbin/smail
10878 </example> The <tt>--package smailwrapper</tt> ensures that
10879 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10880 can bypass the diversion and get installed as the true version.
10881 It's safe to add the diversion unconditionally on upgrades since
10882 it will be left unchanged if it already exists, but
10883 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10884 message, make the command conditional on the version from which
10885 the package is being upgraded:
10887 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10888 dpkg-divert --package smailwrapper --add --rename \
10889 --divert /usr/sbin/smail.real /usr/sbin/smail
10891 </example> where <tt>1.0-2</tt> is the version at which the
10892 diversion was first added to the package. Running the command
10893 during abort-upgrade is pointless but harmless.
10897 The postrm has to do the reverse:
10899 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10900 dpkg-divert --package smailwrapper --remove --rename \
10901 --divert /usr/sbin/smail.real /usr/sbin/smail
10903 </example> If the diversion was added at a particular version, the
10904 postrm should also handle the failure case of upgrading from an
10905 older version (unless the older version is so old that direct
10906 upgrades are no longer supported):
10908 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10909 dpkg-divert --package smailwrapper --remove --rename \
10910 --divert /usr/sbin/smail.real /usr/sbin/smail
10912 </example> where <tt>1.02-2</tt> is the version at which the
10913 diversion was first added to the package. The postrm should not
10914 remove the diversion on upgrades both because there's no reason to
10915 remove the diversion only to immediately re-add it and since the
10916 postrm of the old package is run after unpacking so the removal of
10917 the diversion will fail.
10921 Do not attempt to divert a file which is vitally important for
10922 the system's operation - when using <prgn>dpkg-divert</prgn>
10923 there is a time, after it has been diverted but before
10924 <prgn>dpkg</prgn> has installed the new version, when the file
10925 does not exist.</p>
10930 <!-- Local variables: -->
10931 <!-- indent-tabs-mode: t -->
10933 <!-- vim:set ai et sts=2 sw=2 tw=76: -->